Process cartridge, electrophotographic image forming apparatus, driving force transmission part, and electrophotographic photosensitive drum

ABSTRACT

An electrophotographic image forming apparatus for forming an image on a recording material includes an electrophotographic photosensitive drum; a charging device for charging the photosensitive drum; a developing device for developing a latent image formed on the photosensitive drum into a toner image; a transfer device for transferring the toner image onto the recording material; a fixing device for fixing the toner image on the recording material; a motor; a main assembly side gear for receiving driving force from the motor; a twisted hole formed substantially at a center of the gear, the hole having a polygonal cross-section; a twisted prism projection provided at a longitudinal end of the photosensitive drum, wherein when the main assembly side gear rotates with the hole and projection engaged with each other, rotational driving force is transmitted from the gear to the photosensitive drum through the hole and the projection with the projection being pulled into the hole; and a moving device for imparting relative movement between the hole and the projection in a longitudinal direction of the photosensitive drum.

FIELD OF THE INVENTION

The present invention relates to a process cartridge, anelectrophotographic image forming apparatus, a driving forcetransmission part and an electrophotographic photosensitive drum. Here,the electrophotographic image forming apparatus means an apparatus usingan electrophotographic image formation type process to form an image ona recording medium. Examples of the electrophotographic image formingapparatus include an electrophotographic copying machine, anelectrophotographic printer (laser beam printer, LED printer or thelike), a facsimile device and a word processor.

DESCRIPTION OF THE RELATED ART

Here, the process cartridge may be a cartridge which is detachablymountable to a main assembly of an image forming apparatus and whichcontains as a unit an electrophotographic photosensitive member and atleast one one of process means such as charging means, developing means,cleaning means or the like. The process cartridge may be a cartridgewhich is detachably mountable to a main assembly of an image formingapparatus and which contains as a unit an electrophotographicphotosensitive member and a process means such as charging means,developing means, cleaning means or the like. The process cartridge maybe a cartridge which is detachably mountable to a main assembly of animage forming apparatus and which contains as a unit anelectrophotographic photosensitive member and developing means. Sincethe process cartridge is detachably mountable relative to the mainassembly of the device, the maintenance of the device is easy.

An electrophotographic image forming apparatus using theelectrophotographic image formation type is such that a latent image isformed by selectively exposing the electrophotographic photosensitivemember uniformly charged by charging means to image information light.The latent image is developed with toner by a developing means into atoner image. The toner image thus formed is transferred onto a recordingmedium by transferring means to form an image on the recording material.

Various methods have been proposed to rotate the electrophotographicphotosensitive drum.

In one method, as disclosed in U.S. Pat. No. 5,023,660, pins fixed on aside surface of the gear provided on the main assembly are engaged withrecesses formed in a side surface of a gear provided in thephotosensitive drum, by which the photosensitive drum is rotated.

In another method, as disclosed in U.S. Pat. No. 4,829,335, a helicalgear provided in the main assembly and the helical gear provided on thephotosensitive drum are engaged to rotate the photosensitive drum.

These methods are both very effective for transmitting the rotationforce to the photosensitive drum. The present invention is a further andfundamental improvement of the conventional methods and structures.

SUMMARY OF THE INVENTION

Accordingly, it is a principal object of the present invention toprovide a process cartridge, an electrophotographic image formingapparatus, a driving force transmission part, and an electrophotographicphotosensitive drum, wherein rotation accuracy of theelectrophotographic photosensitive drum is improved.

It is another object of the present invention to provide a processcartridge, an electrophotographic image forming apparatus, a drivingforce transmission part, and an electrophotographic photosensitive drum,wherein the driving force is transmitted to the electrophotographicphotosensitive drum from the main assembly assuredly.

It is a further object of the present invention to provide a processcartridge, electrophotographic image forming apparatus, driving forcetransmission part, and an electrophotographic photosensitive drum,wherein the rotation center of a coupling of the main assembly of thedevice is made concentric with the rotation center of a coupling of theelectrophotographic photosensitive drum when the driving force istransmitted (upon an image forming operation).

It is a further object of the present invention to provide a processcartridge, an electrophotographic image forming apparatus, a drivingforce transmission part and an electrophotographic photosensitive drum,wherein the positioning of the process cartridge relative to the deviceis improved by pulling the electrophotographic photosensitive drum intothe main assembly side when the driving force is transmitted.

It is a further object of the present invention to provide a processcartridge, an electrophotographic image forming apparatus, a drivingforce transmission part, and an electrophotographic photosensitive drum,wherein an image quality is improved.

It is a further object of the present invention to provide a processcartridge, an electrophotographic image forming apparatus, a drivingforce transmission part, and an electrophotographic photosensitive drum,wherein the connection in the driving force transmission mechanismbetween the main assembly and the process cartridge is broken when thedriving force is not transmitted (non-image-formation period), so thatthe operativity in demounting the process cartridge from the mainassembly is improved.

According to an aspect of the present invention, there is provided aprocess cartridge detachably mountable to a main assembly of an imageforming apparatus for forming an image on a recording material, saidmain assembly including a motor, a driving rotatable member forreceiving driving force from said motor and a twisted recess orprojection having a non-circular cross-section and substantially coaxialwith a rotation axis of said drive rotatable member, comprising: arotatable image bearing member; process means actable on saidphotosensitive drum; and a twisted projection or recess provided at alongitudinal end of said image bearing member, having a non-circularcross-section and substantially coaxial with a rotation axis of saidimage bearing member, wherein said projection or recess of said imagebearing member has such a dimension and configuration that it can take afirst relative rotational position with respect to said recess orprojection of said driving rotatable member in which relative rotationalmovement therebetween is permitted, and a second relative rotationalposition with respect to said recess or projection of said drivingrotatable member in which relative rotational movement is prevented inone rotational direction, while the rotation axis of said drivingrotatable member and the rotation axis of said image bearing member aresubstantially aligned.

According to another aspect of the present invention, there is providedan electrophotographic image forming apparatus for forming an image on arecording material, comprising: an electrophotographic photosensitivedrum; charging means for charging said photosensitive drum; developingmeans for developing a latent image formed on said photosensitive druminto a toner image; transfer means for transferring the toner image ontothe recording material; fixing means for fixing the toner image on therecording material; a motor; a main assembly side gear for receivingdriving force from said motor; a twisted hole formed substantially at acenter of said gear, said hole having a polygonal cross-section; atwisted prism projection provided at a longitudinal end of saidphotosensitive drum, wherein when said main assembly side gear rotateswith said hole and projection engaged with each other, rotationaldriving force is transmitted from said gear to said photosensitive drumthrough said hole and said projection with said projection being pulledinto said hole; and moving means for imparting relative movement betweensaid hole and said projection in a longitudinal direction of saidphotosensitive drum.

According to another aspect of the present invention, there is provideda process cartridge detachably mountable to a main assembly of an imageforming apparatus, wherein said main assembly includes a motor, a mainassembly side gear for receiving driving force from said motor and atwisted hole formed substantially at a center of said gear, said holehaving a polygonal cross-section; an electrophotographic photosensitivedrum; process means actable on said photosensitive drum; and a twistedpolygonal prism projection provided at a longitudinal end of saidphotosensitive drum, wherein when said main assembly side gear rotateswith said hole and projection engaged with each other, rotationaldriving force is transmitted from said gear to said photosensitive drumthrough said hole and said projection with said projection being pulledinto said hole.

According to another aspect of the present invention, there is providedan electrophotographic image forming apparatus, for forming an image ona recording material, to which a process cartridge is detachablymountable comprising: a motor; a main assembly side gear for receivingdriving force from said motor; a twisted hole formed substantially at acenter of said gear, said hole having a polygonal cross-section; meansfor mounting a process cartridge which includes: an electrophotographicphotosensitive drum; process means actable on said photosensitive drum;a twisted polygonal prism projection provided at a longitudinal end ofsaid photosensitive drum, wherein when said main assembly side gearrotates with said hole and projection engaged with each other,rotational driving force is transmitted from said gear to saidphotosensitive drum through said hole and said projection with saidprojection being pulled into said hole; and said apparatus furthercomprising; moving means for imparting relative movement between saidhole and said projection in a longitudinal direction of saidphotosensitive drum; and means for feeding the recording material.

According to another aspect of the present invention, there is provideda drive transmission part for transmitting driving force to anelectrophotographic photosensitive drum and a developing roller fordeveloping a latent image formed on said photosensitive drum, which arecontained in a process cartridge detachably mountable to a main assemblyof an image forming apparatus for forming an image on a recordingmaterial, said main assembly including a motor, a main assembly sidegear for receiving driving force from said motor, and a twisted holeformed substantially at a center of said gear, said hole having apolygonal cross-section; a gear for transmitting driving force to saiddeveloping roller from said main assembly to said developing roller whensaid process cartridge is mounted to the main assembly; a shaft providedsubstantially at a center of said gear; and a twisted polygonal prismprojection provided at an end of said shaft, wherein said projectionreceives driving force from the main assembly through engagement betweensaid hole and projection, wherein the driving force is transmitted tosaid photosensitive drum through the shaft, and is transmitted to saiddeveloping roller through said gear.

According to another aspect of the present invention, there is provideda photosensitive drum, which is contained in a process cartridgedetachably mountable to a main assembly of an image forming apparatusfor forming an image on a recording material, said main assemblyincluding a motor, a main assembly side gear for receiving driving forcefrom said motor, and a twisted hole formed substantially at a center ofsaid gear, said hole having a polygonal cross-section; a cylinder havinga photosensitive layer thereon; a drive transmission member mounted toan end of said cylinder, said transmission member including: a gear fortransmitting driving force to said developing roller from said mainassembly to said developing roller when said process cartridge ismounted to the main assembly; a shaft provided substantially at a centerof said gear; and a twisted polygonal prism projection provided at anend of said shaft, wherein said projection receives driving force fromthe main assembly through engagement between said hole and projection,wherein the driving force is transmitted to said photosensitive drumthrough the shaft, and is transmitted to said developing roller throughsaid gear.

In the foregoing the recess and projection may be exchanged with eachother.

These and other objects, features and advantages of the presentinvention will become more apparent upon a consideration of thefollowing description of the preferred embodiments of the presentinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an electrophotographic image formingapparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a process cartridge according to anembodiment of the present invention.

FIG. 3 is perspective view a process cartridge according to anembodiment of the present invention.

FIG. 4 is a perspective view of a process cartridge according to anembodiment of the present invention.

FIG. 5 is a perspective view of a process cartridge mounting portion ofa main assembly of an electrophotographic image forming apparatusaccording to an embodiment of the present invention.

FIG. 6 is a perspective view of a process cartridge mounting portion ofa main assembly of an electrophotographic image forming apparatusaccording to an embodiment of the present invention.

FIG. 7 is a perspective view of a drum flange(driving force transmissionpart) according to an embodiment of the present invention.

FIG. 8 is a perspective view of a photosensitive drum according to anembodiment of the present invention.

FIG. 9 is a sectional view of a process cartridge side coupling portionaccording to an embodiment of the present invention.

FIG. 10 is a perspective view of a coupling portion of a processcartridge according to an embodiment of the present invention.

FIG. 11 is a sectional view of a driving system of a main assembly of anelectrophotographic image forming apparatus according to an embodimentof the present invention.

FIG. 12 is a sectional view of a driving system of a main assembly of anelectrophotographic image forming apparatus according to an embodimentof the present invention.

FIG. 13 is a perspective view of a coupling of a main assembly of thedevice and a coupling of the process cartridge, according to anembodiment of the present invention.

FIG. 14 is a perspective view of a coupling of a main assembly of adevice and a coupling of a process cartridge according to an embodimentof the present invention.

FIG. 15 is a sectional view of a structure of a coupling portion and acover of the main assembly of the device according to an embodiment ofthe present invention.

FIG. 16 is a side view of a structure of a female coupling shaftaccording to an embodiment of the present invention.

FIG. 17 is a side view of a structure of a female coupling shaft uponprocess cartridge mounting-and-demounting relative to the main assemblyaccording to an embodiment of the present invention.

FIGS. 18(a) and 18(b) are sectional views of a recess and a couplingprojection according to an embodiment of the present invention.

FIGS. 19(a) and 19(b) are sectional views of a coupling projectionaccording to an embodiment of the present invention.

FIG. 20 is a sectional view of a process cartridge side coupling portionaccording to an embodiment of the present invention.

FIG. 21 is a sectional view of an electrophotographic image formingapparatus according to an embodiment of the present invention.

FIG. 22 is a perspective view of a recess and a coupling projectionaccording to an embodiment of the present invention.

FIG. 23(a) is a cross-sectional view and FIG. 23(b) is a top plan viewof a male shaft in the form of a twisted triangular prism provided onthe process cartridge and an engageable female shaft provided in themain assembly of a device, according to an embodiment of the presentinvention.

FIG. 24 is a perspective view of a twisted recess having a cross-sectionin the form of a triangle shape on the process cartridge, and aprojection in the form of a complementary twisted triangular prism inthe main assembly of the device, according to an embodiment of thepresent invention.

FIG. 25 is a perspective view of a driving mechanism of the coupling ofFIG. 24.

FIGS. 26(a) and 26(b) illustrate an interrelation mechanism of a drivingmeans and an openable cover according to an embodiment of the presentinvention.

FIGS. 27(a) and 27(b) illustrate an interrelation mechanism of drivingmeans and an openable cover according to an embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described in conjunctionwith the accompanying drawings.

Embodiment 1

Referring to FIG. 1 to FIG. 10, the description will be made as to aprocess cartridge and an electrophotographic image forming apparatus towhich it is detachably mountable according to embodiment 1. In thefollowing description, the general arrangement of the process cartridgeand the electrophotographic image forming apparatus usable therewithwill be first described referring to FIG. 1 to FIG. 6, and then thestructure of a coupling of a driving force transmission mechanismbetween the process cartridge and the image forming apparatus will bedescribed, referring to FIG. 7 to FIG. 10.

General Arrangement

FIG. 1 is a schematic view of the electrophotographic image formingapparatus A to which the process cartridge is mounted; FIG. 2 is across-sectional view of the process cartridge B; FIGS. 3 and 4 areperspective views of an outer appearance of the process cartridge; andFIGS. 5 and 6 illustrate device structures for mounting the processcartridge to the main assembly of the device.

In this electrophotographic image forming apparatus (laser beam printerin the embodiment), as shown in FIG. 1, an electrophotographicphotosensitive member 7 of a drum configuration is exposed to a laserbeam based on image information supplied from an optical system 1 sothat a latent image is formed on the photosensitive member, and thelatent image is developed with toner into a toner image. In synchronismwith the formation of the toner image, a recording medium 2 (recordingsheet or the like) is fed from a feeding cassette 3a by transportingmeans 3 comprising pick-up rollers 3b, feeding rollers 3c, feedingrollers 3d, registration rollers 3e or the like. The toner image formedon the photosensitive drum 7 is transferred onto the recording medium 2by voltage application to the transfer roller 4 as transferring means.The recording medium 2 is guided by a guide plate 3f to a fixing means5. The fixing means 5 comprises a fixing roller 5c comprising a drivingroller 5a and a heater 5b, and applies heat and pressure to therecording medium 2 to fix the transferred toner image onto the recordingmedium 2. The recording medium 2 is fed by the discharging rollers 3gand 3w, and is discharged to the discharging portion 6 through areversion feeding path. In the image forming apparatus A, manual sheetfeeding is possible using a manual feed tray and roller 3j.

The process cartridge B contains the electrophotographic photosensitivemember and at least one process means. The process means includes, forexample, charging means for charging the electrophotographicphotosensitive member, developing means for developing the latent imageon the electrophotographic photosensitive member, and cleaning means forremoving the residual toner from the surface of the electrophotographicphotosensitive member.

The process cartridge B of this example contains a photosensitive drum7, the charging roller 8, the exposure opening 9, and the developingmeans 10, as shown. The electrophotographic photosensitive drum 7 in theprocess cartridge B is rotated through a coupling mechanism by the mainassembly 13 of the device, as will be described hereinafter. The surfaceof the photosensitive drum is subjected to uniform charging by voltageapplication from the charging roller 8 which is a charging means, andthe information light from the optical system 1 is projected onto thephotosensitive drum 7 through an exposure opening 9 to form a latentimage, which is developed by the developing means 10.

In the developing means 10, the toner in a toner accommodating portion10a is fed out by rotation of a feeding member 10b. A developing roller10d containing a fixed magnet 10c is rotated so that a toner layerhaving triboelectric charge provided by a development blade 10e isformed on the surface of the developing roller 10d. The toner istransferred to the photosensitive drum 7 in accordance with the latentimage to form the toner image (visualization). The toner image istransferred onto the recording medium 2 by application of the voltage ofthe opposite polarity from the toner image to the transfer roller 4provided in the main assembly 13 of the device. The photosensitive drum7 after transfer is cleaned by the cleaning means 11 so that theresidual toner is removed. More particularly, the toner is scraped offby the cleaning blade 11a. The toner thus removed is collected in aresidual toner container 11c by a receptor sheet 11b.

The charging roller 8 is contacted to the photosensitive drum 7 and isdriven by the photosensitive drum 7. The cleaning blade 11a is contactedto the photosensitive drum 7.

The process cartridge B comprises a toner frame 12a having a toneraccommodating portion 10a accommodating toner and a developing frame 12bsupporting a developing member such as a developing roller 10d, whichframes are welded together (ultrasonic welding in this example) to forma developing unit. This developing unit is swingably coupled with acleaning frame 12c supporting the photosensitive drum 7, the chargingroller 8, the cleaning means 11 and the like. The process cartridge B ismounted to a cartridge mounting means of the main assembly 13 of thedevice by a user in a direction crossing with a longitudinal directionof the photosensitive drum 7 (FIGS. 5 and 6). The cleaning frame 12c isprovided with mounting guides 12c 4 adjacent a bearing 12c 2. Thebearing 24 (projection 24a) mounted to the cleaning frame 12c isprovided with a guide 24c. the bearing 24, projection 24a and guide 24care integrally molded. The mounting guides 24c is guided by guides 15aand 15b when the process cartridge B is mounted.

As cartridge mounting means, as shown in FIG. 5, cartridge mountingguiding members 15 are mounted opposed to each other on left and rightsides of a cartridge mounting space of the main assembly 13 (one side inFIG. 5 and the other side in FIG. 6). The guiding members 15 have guideportions 15a and 15c opposed to each other to function as guides whenthe process cartridge B is pushed into the main assembly. The processcartridge is inserted while bosses or the like projected from oppositelongitudinal ends of the cartridge frame are guided by the guideportions 15a and 15c. When the process cartridge B is to be mounted tothe main assembly 13, a cover 14 which is openable about a shaft 14a isopened. By closing the openable cover 14, the process cartridge B iscorrectly mounted to the image forming apparatus A. When the processcartridge B is taken out from the main assembly 13, the openable cover14 is opened.

When the process cartridge B is mounted to the image forming apparatusA, the cartridge side coupling and the main assembly side coupling arecombined in interrelation with the closing operation of the openablecover 14, as will be described hereinafter, so that the photosensitivedrum 7 and the like can receive the driving force from the mainassembly.

Coupling and Driving Structure

The description will be made as to the structure of the coupling meanswhich is a driving force transmission mechanism for transmitting thedriving force to the process cartridge B from the main assembly 13 ofthe image forming apparatus.

FIG. 7 is a perspective view of a drum flange 16 as a driving forcetransmission part having an integrally formed male shaft 17; FIG. 8 is apartly sectional perspective view of the photosensitive drum 7 having adrum flange 16 mounted thereto; FIG. 9 is a sectional view wherein thephotosensitive drum 7 is mounted to the process cartridge B; FIG. 10 isan enlarged perspective view of the male shaft 17 of the processcartridge B of FIG. 9; FIG. 11 shows a relation between the male shaft17 (provided to the process cartridge B) and the female shaft 18(provided to the main assembly 13).

As shown in FIG. 8 to FIG. 11, there is provided a cartridge sidecoupling means at a longitudinal end of the photosensitive drum 7 in theprocess cartridge B. The coupling means has a male coupling shaft 17(circular column configuration) mounted to the drum flange 16 fixed toan end of the photosensitive drum 7. Here, the end surface of theprojection 17a is parallel with the end surface of the projection shaft17. The male shaft 17 is engaged with a bearing 24 and functions as adrum rotational shaft. In this example, the flange 16, male couplingshaft 17 and the projection 17a are integrally formed. The flange 16 isprovided with a helical gear 16a for transmitting the driving force tothe developing roller 10d in the process cartridge. Therefore, as shownin FIG. 7, the drum flange 16 is an integrally molded member having thehelical gear 16a, the male shaft 17 and the projection 17a, and is adriving force transmission part having the function of transmitting thedriving force.

The projection 17a has a twisted polygonal prism configuration, moreparticularly, the configuration resulting from twisting a substantiallyequilateral triangular prism in the rotational direction. The recess 18ais a polygonal shape twisted in the rotational direction of the shaftand therefore is engageable with or complimentary with the projection17a. The recess 18a has a section of a substantially equilateraltriangle. The recess 18a integrally rotates with the gear 34 of the mainassembly 13. In the structure of this example, the process cartridge Bis mounted to the main assembly 13, and the projection 17a and therecess 18a of the main assembly 13 are engaged. When the rotation forceis transmitted from the recess 18a to the projection 17a, the apexes ofthe projection 17a of the equilateral triangle are contacted regularlywith the inside surfaces of the recess 18a, and therefore, the centersthereof are automatically aligned by the rotation, as will be understoodfrom FIGS. 8(a) and (b). Further, the force in the direction of pullingdeviating the projection 17 to the recess 18 is produced during rotationdue to the twisting directions thereof, so that the end surface 17a1 ofthe projection is contacted to the recess 18a1. Since the photosensitivedrum 7 is integral with the projection 17a, the axial position andradial position there are correctly determined in the main assembly 13of the image forming apparatus.

In this example, as seen from the photosensitive drum 7, the directionof twisting of the projection 17a is opposite from the rotationdirection of the photosensitive drum 7 away from the base portion of theprojection toward the end portion thereof. The direction of twisting ofthe recess 18a is opposite therefrom away from the inlet portion of therecess 18a toward the inside. The direction of twisting of the helicalgear 16a of the drum flange 16, which will be described hereinafter, isopposite from the twisting direction of the projection 17a.

As shown in FIG. 18, the projection 17a and the recess 18a satisfyd1<d0<d2, where d0 is a diameter of a circumscribed circle R0 of thetriangular prism of the projection 17a, d1 is a diameter of an inscribedcircle R1 of the space in the form of triangle of the recess 18a, and d2is a diameter of a circumscribed circle R2 of the triangle.

Preferable examples of the numerical ranges of the diameters are asfollows:

d0=approx. 3 mm-70 mm

d1=approx. 3 mm-70 mm

d2=approx. 3 mm-70 mm.

In these ranges, the sizes are selected so as to satisfy theabove-described relations.

In this example, the sizes are as follows:

d0=approx. 16 mm

d1=approx. 9.5 mm

d2=approx. 17.5 mm.

The degree or amount of the twisting of the projection 17a is approx.1°-15° per 1 mm of the axial length of the projection 17a in therotational direction. More particularly, in this example, it is twistedat approx. 7.5° per 1 mm of the axial length.

However, the present invention is not limited to these values.

The position of a cross-section of a three dimensional member isdetermined by three contact points, theoretically. When theconfigurations of the projections 17a and the recesses 18a aresubstantially an equilateral triangular, the apexes of the projection17a are contacted to the inside surfaces of the equilateral triangleunder the same conditions. Therefore, the changes of the contact pointsand the rotation non-uniformity of the coupling driving due to the loadvariation during the rotation of the process cartridge B are minimized,thus improving the rotation accuracy of the photosensitive drum 7 (FIG.18). The male shaft 17 and projection 17a are provided on the drumflange 16 so that when the drum flange 16 is mounted to an end of thephotosensitive drum 7, it is aligned with the axis of the photosensitivedrum 7. Designated by 16b is an engaging portion which is engaged withan inside surface of the drum cylinder 7a when the drum flange 16 ismounted to the photosensitive drum 7. The drum flange 16 is mounted tothe photosensitive drum 7 by cramping, bonding or the like. The outersurface of the drum cylinder 7a is coated with a photosensitive material7b (FIGS. 8 and 9 reference).

A drum flange 25 is fixed to the other end side of the photosensitivedrum 7. The drum flange 25 has a drum shaft 25a and spur gear 25bintegrally formed therewith.

When the process cartridge B is mounted to the main assembly 13 of theapparatus, the drum shaft 25a (bearing 12c2) is engaged with an U groove15b (FIG. 5) of the main assembly 13 of the apparatus so as to becorrectly positioned, and the spur gear 25b integrally molded with theflange 25 is meshed with a gear (shown) for transmitting the drivingforce to the transfer roller 4.

Examples of the material of the drum flange 16 include polyacetal,polycarbonate and polyamide, polybutylene terephthalate, or anotherresin material. Other materials are usable.

Around the projection 17a of the male coupling shaft 17 of the processcartridge B, a circular projection 24a coaxial with the male shaft 17 isprovided on the cleaning frame 12c (FIGS. 3 and 9). The projection 24afunctions to protect the coupling projection 17a when, for example, theprocess cartridge B is mounted or demounted relative to the mainassembly, so that the coupling projection 17a is prevented from beingdamaged or deformed by external force or the like. Thus, the vibrationor wobbles during the coupling driving operation due to the damage ofthe projection 17a, can be avoided.

The projection 24a also can function as a guiding member for themounting and demounting of the process cartridge B relative to the mainassembly 13 of the image forming apparatus. More particularly, when theprocess cartridge B is mounted to the main assembly A, the projection24a is contacted to the main assembly side guide portion 15c andfunctions to guide the process cartridge B to the mounting position ofthe apparatus, thus facilitating the mounting-and-demounting of theprocess cartridge B relative to the main assembly 13. When the processcartridge B is mounted to the mounting position, the projection 24a issupported by the recess 15d provided on the guide portion 15c. When themale coupling shaft 17 and female shaft 18 are aligned by the drivingfor the image formation, the projection 24a is raised slightly from theU groove 15d (approx. 0.3 mm-1.0 mm), and the gap between the projection24a and the main assembly guide portion 15a (recess 15d) is smaller thanthe gap between the coupling projection 17a and the recess 18a in theradial direction. Therefore, the engagement between the couplingprojection 17a and the recess 18a are permitted while the processcartridge B is mounted to the main assembly 13. A recess 18a is providedopposed to the U groove 15d. The configuration of the projection 24a isnot limited to circular as in this example, but may be any, for example,arcuate configuration, if it is guided by the guide portion 15c, and issupported by the U groove 15d. In this example, the bearing 24 forsupporting rotatably the shaft portion 17 and the circular projection24a are integrally molded, and are fixed to the cleaning frame 12c byscrews (FIG. 9), but the bearing 24 and the projection 24a may beseparate members.

In this example, the drum shaft 25a is engaged with the bearing portion12c2 provided in the cleaning frame 12c (FIG. 9), and the male shaft 17is engaged to the inside surface of the bearing 24 provided in thecleaning frame 12c, and with this state, the photosensitive drum 7 ismounted to the cleaning frame 12c of the process cartridge B. Therefore,the photosensitive drum 7 is rotated about the shaft 17 and 25a. In thisexample, the photosensitive drum 7 is mounted to the cleaning frame 12cin the manner that the movement thereof in the axial direction ispossible. This is done in consideration of the mounting tolerance. Thisstructure is not inevitable, and the photosensitive drum 7 may benon-movable in the slide direction.

Among the photosensitive drum 7, the flange 16 and the male couplingshaft 17, there is a relationship as shown in FIG. 9. More particularly,the outer diameter of the photosensitive drum 7 (outer diameter of thecylinder 7a)=D1, the helical gear dedendum circle diameter=G, thediameter of the photosensitive drum bearing (outer diameter of the shaftportion 17, the inner diameter of the bearing 24)=F, the diameter=C ofthe circumscribed circle of the coupling projection, and the engagingportion diameter (drum inner diameter)=D2 of the drum flange 16 relativeto the photosensitive drum 7, satisfy D1>F≧C and G>D2.

The D1>F is effective to reduce the torque required by the sliding loadat the bearing. The F≧C is effective to simplify the mold structure whenthe flange portion is molded since the undercut portion is not requiredwhich otherwise is required in the mold division of the mold in thedirection of the arrow H in the Figure.

Furthermore, because G>D2 is satisfied, the mold configuration of thegear portion is on the left side mold in FIG. 6, and therefore, theright side mold structure which is complicated due to the provision ofthe coupling configuration is simplified, and therefore, the durabilityof the mold is improved.

The dimensional relations apply in the case that the relation betweenthe male shaft 17 and the female shaft 18 are reversed, that is, in thecase that the photosensitive drum is provided with the recess 18a whilethe main assembly side of the apparatus is provided with the projection17a (the diameter of the circumscribed circle of the polygonal of therecess 18a is C). The same advantages are provided in such a case, too.

Examples of the numerical ranges of them are as follows:

D1=approx. 10 mm-60 mm

G=approx. 10 mm-70 mm

F=approx. 5 mm-70 mm

C=approx. 3 mm-70 mm

D2=approx. 9 mm-59 mm.

The sizes may be selected within these ranges so as to satisfy theabove-described relations.

In this example, sizes are as follows:

D1=approx. 30 mm

G=approx. 31 mm

F=approx. 16 mm

C=approx. 14 mm.

However, the present invention is not limited to these sizes.

On the other hand, the main assembly 13 of the image forming apparatusis provided with main assembly coupling means. The main assemblycoupling means includes a female coupling shaft 18 (circular columnconfiguration) at a position in alignment with the photosensitive drumrotation axis when the process cartridge B is inserted. The femalecoupling shaft 18 is a driving shaft integral with the large diametergear 34 for transmitting the driving force from the motor 30 to thephotosensitive drum 7, as shown in FIG. 12. The female shaft 18 isprojected from a lateral edge of the gear 34 at a rotation center of thegear 34 (FIGS. 13 and 14). In this example, the large diameter gear 34and the female coupling shaft 18 are integrally molded.

The gear 34 in the main assembly side is a helical gear. A tooth thereofhas such an inclination angle that a thrust is produced in the directionof moving the female shaft 18 toward the male shaft 17 when the drivingforce is transmitted thereto from the helical gear 20 fixed to the shaft30a of the motor 30. Therefore, when the motor 30 is driven upon imageformation, the thrust is effective to move the female shaft 18 to themale shaft 17 to establish firm coupling between the recess 18a and theprojection 17a. The recess 18a is provided at the rotation center of thefemale shaft 18 at an end of the female shaft 18.

In this embodiment, the driving force is transmitted directly from thegear 20 fixed to the motor shaft 30a to the gear 34, however, a geartrain may be used for deceleration and driving transmission, or use maybe made with belt and pulley, a pair of friction rollers or acombination of timing belt and pulley.

Referring to FIG. 15 to FIG. 17, the description will be made as to thestructure for engaging the recess 18a and projection 17a ininterrelation with the closing operation of the openable cover 14.

FIG. 15 is a view as seen in a direction of the axis of thephotosensitive drum 7,.wherein an outer cam 35 and an inner cam 36 (FIG.17) are disposed between the gear 34 and the photosensitive drum 7(unshown), and the cover 14 of the image forming apparatus and the outercam 35 are connected by a rod 37, thus constituting a moving means.Designated by 40 is a side plate provided in the main assembly 13.Referring to FIGS. 16 and 17, designated by 34a is a shaft supportingportion for supporting the gear 34 on the side plate 39.

FIG. 16 is a view as seen from the right side. When the cover 14 isclosed, the rod 37 and the outer cam 35 and so on take the positionshown in this Figure, and they are coupled by the coupling projection17a and the recess 18a to permit driving force transmission from thegear 34 to the photosensitive drum 7. When the cover 14 is opened, thecam 35 is pulled through the rod 37, as shown in FIG. 17, and therefore,the cam 35 is rotated to be contacted to the inner cam 36, thus movingthe gear 34 away from the photosensitive drum 7. At this time, the gear34 and the female coupling shaft 18 are pushed by the outer cam 35 topush the spring 38 mounted between itself and the fixing plate 39 andmoves in the same direction, so that the recess 18a becomes away fromthe projection 17a to release the coupling, by which the cartridge Bdemounting is enabled. When the cover 14 is closed, the cam 35 rotatesin the opposite direction and is pushed by the spring 38 so that thegear 34 is reset to the position shown in FIG. 16 to enable the drivingtransmission. With this structure, the mounting-and-demounting of thecartridge B and the drive transmission are disabled and enabled inresponse to the opening and closing of the cover 14.

In this example, the cover 14 is opened and closed when the processcartridge B is mounted to or demounted from the main assembly of theapparatus. In interrelation with the opening and closing of the cover14, the recess 18a moves in a horizontal direction (arrow j direction).When the process cartridge B is mounted or demounted relative to themain assembly, the coupling (between 17a and 18a) between processcartridge B and the main assembly 13 of the apparatus is assuredlydisengaged. Therefore, the mounting-and-demounting of the processcartridge B relative to the main assembly 13 can be smoothly carriedout. In this example, the recess 18a is urged toward the processcartridge B by the spring 38. Therefore, even if the projection 17a andthe recess 18a are not aligned, and therefore abutment occurstherebetween, and they are not engaged, they are engaged instantaneouslyupon the rotation of the recess 18a.

The description will be made as to the configurations of the projection17a and the recess 18a which are engaging portion of the coupling means.

The female coupling shaft 18 provided in the main assembly 13 is movabletoward the rotational shaft, as described above, but is not movable inthe radial direction. The process cartridge B is mounted in the mainassembly 13 of the apparatus such that it is movable in the longitudinaldirection and radial direction of the photosensitive drum 7.

More particularly, when the process cartridge B is mounted in the mainassembly 13 of the device, a portion of the drum shaft 25a (bearing12c2) (FIGS. 4 and 9) formed on the flange 25 mounted adjacent the otherlongitudinal end of the photosensitive drum 7 is received by the Ugroove 15b (FIG. 5) of the main assembly 13 and is engaged therewithwithout gap, so that it is correctly positioned, and the spur gear 25bintegrally molded with the flange 25 is meshed with a gear (not shown)for transmitting the driving force to the transfer roller 4. On theother hand, at the longitudinal end of the photosensitive drum 7(driving side), the projection 24a of the cleaning frame 12c issupported by the recess 15d of the main assembly 13. By closing thecover 14, the recess 18a is moved in a horizontal direction and isreceived by the projection 17a (FIG. 8 (a)).

The positioning and driving transmission at the driving side (couplingside) are as follows.

When the main assembly driving motor 30 is rotated, the female couplingshaft 18 is moved toward the male coupling shaft 17 (arrow d in FIG.13), and they are engaged when the phases of the projection 17a and therecess 18a are matched (in this example, since the projection 17a andrecess 18a have substantially equilateral triangular configurations, thephases thereof match at every 120°). Then the rotation force istransmitted from the main assembly 13 of the apparatus to the processcartridge B (from the state of FIG. 17 to the state of FIG. 16).

Since the sizes of the equilateral triangles are different, moreparticularly, the size of the triangle of the recess 18a is larger thanthat of the projection 17a (as shown in FIG. 8 (a)), the projection 17ais smoothly engaged into the recess 18a with the gap therebetween. Theaccuracy of the positioning between the male coupling shaft 17 andfemale coupling shaft 18 may be rough at the time of the engagingaction.

In this example, the projection length of the circular projection 24a islarger than that of the projection 17a (FIG. 9). Therefore, when theprojection 17a and the recess 18a are engaged, the inside surface of thecircular projection 24a is engaged with the outer peripheral surface ofthe female coupling shaft 18 to guide the engagement therebetween.

When the female coupling shaft 18 is rotated with the projection 17aengaged with the recess 18a for image formation, the inside surfaces18a1 of the recess 18a are engaged to the apex lines 17a1 of theequilateral triangular prism of the projection 17a (as shown in FIG. 8)to permit the transmission of the driving force. At this time, the maleshaft 17 instantaneously moves so that the inside surfaces 18a1 of therecess 18a are contacted to the edge lines 17a1 of the projection 17a atregular positions (equidistantly) from the state of FIG. 8 (a) to thestate of FIG. 8 (b). Since the projection 17a and the recess 18a areboth substantially equilateral triangles, the male shaft 17 and thefemale shaft 18 are brought into the coaxial state with each other withuniform contact forces. Immediately after the projection 17a is broughtinto engagement with the recess 18a, the rotation center of theprojection 17a is not aligned with the rotation center X2 of the recess18a (FIG. 8 (a)). However, when the recess 18a starts to rotate, and itis contacted to the edge line 17a1 of the projection 17a at 3 points(lines), the rotation centers X1 and X2 are substantially aligned.

Thus, the coupling shaft 17 and 18 are automatically axis aligned by therotation of the motor 30 (self-alignment). Furthermore, by the drivingforce transmission to the photosensitive drum 7, the process cartridge Bis rotated, by which the abutment portion 12c1 provided on the topsurface of the cleaning frame 12c of the process cartridge B (FIGS. 3and 4) is abutted to the abutment portion 13a (FIG. 1) fixed to the mainassembly 13 of the image forming apparatus, so that the processcartridge B is precisely positioned to the main assembly A of the imageforming apparatus.

When the process cartridge is not driven (non-image formation), the gapis provided between the projection 17a and recess 18a in the rotationradius direction (radial direction), the engagement between thecouplings and the mounting and demounting of the process cartridgerelative to the main assembly are made easier. Additionally, the contactforce at the coupling engagement portion is stabilized, so that thewobble and vibration at this position can be suppressed.

In this example, the coupling projection and recess have substantiallyequilateral triangular configurations, but a similar advantage can beprovided if the configuration is an equilateral polygonal. The use of anequilateral polygonal configuration is preferable since the positioningis correct, but any polygonal configurations are usable if theengagement is possible and pulling engagement is possible.

When the comparison is made between the coupling projection and recess,the projection is easily damaged, and the strength thereof is smallerthan the recess. In this example, the coupling projection is provided inthe process cartridge B which is exchangeable, and the coupling recessis provided in the main assembly 13 which is required to have a higherstrength.

The process cartridge B of this embodiment is summarized as follows. Theprocess cartridge B of this example is detachably mountable relative toa main assembly of an electrophotographic image forming apparatus Acomprising a motor 30, a main assembly gear 34 for receiving the drivingforce from the motor, and a twisted polygonal hole 18a integrallyrotatable with the main assembly gear, the hole being formed at thecenter of the main assembly gear, the electrophotographic image formingapparatus A being capable of forming an image on the recording medium 2.The process cartridge comprises the electrophotographic photosensitivedrum 7, the process means actable on the electrophotographicphotosensitive drum (charging roller 8, developing roller 10, cleaningblade 11a), and a twisted polygonal prism projection (projection 17a)engageable with the twisted polygonal hole of the main assembly, theprojection is being provided at the end of the electrophotographicphotosensitive drum. The process cartridge B is mounted to the mainassembly 13 of the main assembly, and the polygonal prism projection 17ais engaged with the recess of the main assembly, and when the gear 34 isrotated, the rotational driving force is transmitted to thephotosensitive drum.

The projection 17a is projected from the end of the shaft portion 17projected outwardly in the longitudinal direction of the drum from therotation center position of the drum 7. The shaft portion functions torotatably support the drum 7 on the cartridge frame 12c.

The shaft portion 17 is provided at the central portion of the helicalgear 16a, and at the opposite end from the helical gear 16a side, anengaging portion 16b for engagement with the inside surface of theelectrophotographic photosensitive drum 7 is provided. The projection17a, the shaft portion 17, the helical gear 16a, and the engagingportion 16b are integrally molded of a resin material. The helical gearfunctions to transmit the rotation force to the developing roller 10a asthe process means.

Furthermore, there is provided a circular outer wall 24a enclosing thepolygonal prism projection 17a, or an arcuate configuration outer wallalong a part of the polygonal prism projection. The outer wall 24afunctions as a guide for the engagement between the hole 18a and theprojection 17a by relative movement therebetween.

The outer diameter D1 of the electrophotographic photosensitive drum 7,the outer diameter F of the shaft portion 17, and the diameter C of thecircumscribed circle of the polygonal prism projection 17a, satisfyD1>F≧C.

The outer diameter F of the shaft portion 17, the diameter C of thecircumscribed circle of the polygonal prism projection 17a, the dedendumdiameter G of the gear 16a of the electrophotographic photosensitivedrum 7, and the inner diameter D2 of the electrophotographicphotosensitive drum 7, satisfy G>D2 and G>F≧C.

The outer diameter D1 of the electrophotographic photosensitive drum 7,and the dedendum circle diameter L of the main assembly gear 34, L ispreferably not less than approx. 1.0 times D1 and not more than 5.0times D1. The relation is properly selected by one skilled in the art inconsideration of the space of the main assembly of the device and thedesired image quality. The dimensions are not limiting. In this example,it is approx. 3 times.

The module of the main assembly gear 34 is approx. 0.4-0.7. The dedendumdiameter L of the main assembly gear 34 of the device is approx. 30mm-150 mm, and the number of teeth of the main assembly gear 34 isapprox. 40 teeth to 400 teeth. They are properly selected by one skilledin the art in consideration of the space in the main assembly anddesired image quality. The figures are not limiting. In this example,the module of the gear 34 is approx. 0.5, and L is approx. 100 mm, andthe number of the teeth of the gear 34 is 200 teeth.

The positioning of the process cartridge B relative to the main assembly13 during the image formation (driving transmission) is summarized asfollows.

First, the process cartridge B is positioned by the bearing 12 beingsnugly fitted in the U groove 15d during the non-image formation. On theother hand, the projection 24a is simply supported by a receptor portion15c. During the image formation, the process cartridge B is positionedby the projection 17a being attracted by the recess 18a of the mainassembly 13 and being engaged with the projection 17a. Namely, duringthe image formation, the process cartridge B is positioned by the Ugroove 15b at one longitudinal end, and by the recess 18a at the otherend. In this example, the photosensitive drum 7 is movable in thelongitudinal direction (approx. 0.1 mm-1.0 mm). When the projection 17ais attracted to the recess 18a, the end portion 16c of the drum flange16 (FIGS. 7, 8 and 9) is brought into contact to the end portion 24b ofthe bearing 24. The process cartridge B, which is mounted movablyrelative to the main assembly side plate or mounting guides 15a and 15cwith play of approx. 0.1-3 mm) in consideration of assembly tolerance,is pulled toward the photosensitive drum 7 in the longitudinal directionand in the radial direction, thus moving in an inclined upwarddirection. In the case the end portion 16c is in contact with the endportion 24b at the beginning, or when the photosensitive drum 7 does nothave play in the longitudinal direction, the process cartridge B ispulled to the photosensitive drum 7 immediately in its longitudinaldirection and in the radial direction, thus moving in an upward inclineddirection.

During the image formation operation, the process cartridge B receivesthe rotation force in the same direction as the rotation direction ofthe photosensitive drum 7. By this rotation force, the contact portion12c1 is contacted to the fixed portion 13a.

Accordingly, the process cartridge B is correctly positioned relative tothe main assembly 13 of the apparatus in both the longitudinal directionand the radial direction during the image formation operation.

When the process cartridge B is pushed by an elastic member as in FIG.21 for example, the process cartridge B may not move in the longitudinaldirection of the drum 7, depending on the strength of the elastic forceprovided by the elastic member. Even in that case, when the drivetransmission starts, the process cartridge B moves in the radialdirection (substantially upward) so that it is correctly positionedrelative to the main assembly. In this case, even if the drum 7 does notinvolve play in the longitudinal direction, the process cartridge B iscorrectly positioned relative to the main assembly.

Referring back to FIG. 18, it will be understood that the couplingmechanism is summarized as follows. The driving rotatable member 18a forreceiving driving force from the motor is provided with a twisted recessor projection having a noncircular cross-section and substantiallycoaxial with a rotation axis X2 of the drive rotatable member 18a. Themember to be driven or the image bearing member is provided with atwisted projection or recess 17a provided at a longitudinal end of theimage bearing member, having a non-circular cross-section andsubstantially coaxial with a rotation axis of the image bearing member.The projection or recess of the image bearing member 17a has such adimension and configuration that it can take a first relative rotationalposition (FIG. 18(a), for example) with respect to the recess orprojection of the driving rotatable member 18a in which relativerotational movement therebetween is permitted, and a second relativerotational position (FIG. 18(b), for example) with respect to the recessor projection of the driving rotatable member 18a in which relativerotational movement is prevented in one rotational direction (indicatedby arrows in FIG. 18(b), while the rotation axis X2 of the drivingrotatable member 18a and the rotation axis X1 of the image bearingmember are substantially aligned with each other.

It is preferable that the recess or projection of said driving rotatablemember and the projection or recess of the image bearing member arecontacted substantially at three twisted points (lines). It is furtherpreferable that the three points constitute a substantially equilateraltriangle.

Embodiment 2

Referring to FIG. 19, the description will be made as to embodiment 2 ofthe projection 17a of the male coupling shaft 17. The fundamentalstructures of the process cartridge and the image forming apparatus arethe same as in embodiment 1, and therefore, the same reference numeralsas in embodiment 1 are assigned to the elements having the correspondingfunctions, and detailed descriptions thereof are omitted for simplicity.

The coupling projection 17a of FIG. 19 is different from that inembodiment 1 in that the apexes 17a2 of the substantially equilateralpolygonal prism shape of the projection (it is substantially anequilateral triangle shape in FIG. 19) are beveled. The bevelingincludes rounding as shown in FIG. 19(a) and straight cutting as shownin FIG. 19(b).

With this structure, the collapse of the apexes of the projection 17aduring handling of the process cartridge B can be avoided. During thedriving, the deformation and deflection of the apexes due toinsufficient strength can be avoided. Thus, the decrease of thealignment accuracy between the male shaft 17 and the female shaft 18 canbe prevented, and the wobble and vibration at the coupling portion canbe avoided.

In FIG. 19(a), as will be understood when this configuration isintroduced in the projection 17a of FIG. 18(b), the portions contactedto the inner surface of the recess are not the outermost points of theconfiguration of FIG. 19(a), but are portions slightly deviatedtherefrom (at each apex portion). From the standpoint of axis alignment,it is preferable that such deviated three contact points constitute asubstantially equilateral triangle.

Similarly, in FIG. 19(b), it is preferable that the three pointsconstitute a substantially equilateral triangle.

For the same reason, in a polygonal projection (polygonal recess)example, it is preferable that the projection and recess are contactedat three points which constitute a substantially equilateral triangle,from the standpoint of the axis alignment.

In the case of FIG. 19(a), each contact point (actually a twisted line)in the cross-section may have a certain width. In such a case, thecenters or one side end of the widths are deemed as the points toconstitute the triangle.

Embodiment 3

Referring to FIG. 20, the description will be made as to embodiment 3 ofthe projection of the male coupling shaft 17. The fundamental structuresof the process cartridge and the image forming apparatus aresubstantially the same as in embodiment 1. The same reference numeralsas in embodiment 1 are assigned to the elements having the correspondingfunctions, and detailed descriptions thereof are omitted for simplicity.

In embodiment 1, the flange 16 of the photosensitive drum 7 and the malecoupling shaft 17 are integral, but they may be separate members, whichare incorporated in the process cartridge B, respectively.

When the male coupling shaft 17 and the flange 16 are separate members,as in this example, the male coupling shaft 17 can be mounted into theengaging portion 16b of the flange 16 by press-fitting or the like afterthe photosensitive drum 7 with the flange 16 is incorporated in theframe 12c, so that the photosensitive drum 7 may not be assembled intothe frame 12c in an inclined direction.

Embodiment 4

Referring to FIG. 21, the description will be made as to embodiment 4having a different positioning structure of the process cartridge to themain assembly of the image forming apparatus, using the couplingstructure of the present invention. The fundamental structures of theprocess cartridge and the image forming apparatus are substantially thesame as in embodiment 1. The same reference numerals as in embodiment 1are assigned to the elements having the corresponding functions, anddetailed descriptions thereof are omitted for simplicity.

As shown in FIG. 21, the main assembly 13 of the image forming apparatusis provided with an elastic member 13b for urging the process cartridgeB in the rotation direction of the photosensitive drum 7. The elasticmember 13b is contacted to the contact portion 12c3 of the cleaningframe 12c of the process cartridge B while the process cartridge B is inthe main assembly in place, and it applies the rotation force in thesame direction as the rotation direction of the photosensitive drum 7 tothe process cartridge B. The process cartridge B receiving the rotationforce tends to rotate in the rotation direction of the photosensitivedrum 7 (clockwise direction in FIG. 21), but is stopped by the abutmentbetween the abutment portion 12c1 of the frame 12c and the abutmentportion 13a of the main assembly. This is effective to prevent thevibration, in the rotation direction, of the process cartridge B urgedin the rotation direction of the photosensitive drum 7 by the couplingdriving force, due to the internal load variation or the like. Thecontact portion 12c3 is provided at each of two positions, namely,adjacent one end side and other end side in the longitudinal directionof the photosensitive drum 7 on the top surface of the cleaning frame12c (FIGS. 3 and 4).

Embodiment 5

Referring to FIG. 22, another embodiment of the coupling structure willbe described. The fundamental structures of the process cartridge andthe image forming apparatus are substantially the same as inembodiment 1. The same reference numerals as in embodiment 1 areassigned to the elements having the corresponding functions, anddetailed descriptions thereof are omitted for simplicity.

In this example, as shown in FIG. 22, the projection 17a of the malecoupling shaft 17 and the recess 18a of the female shaft 18 have asubstantially rectangular configuration section which is twisted in therotation direction of the shaft. Similarly to embodiment 1, the durablecoupling recess 18a is provided in the main assembly 13 of the imageforming apparatus. With this structure, when the driving is transmittedwhile the coupling is in engagement, the force is produced so that thefemale coupling shaft 18 pulls the male shaft 17 in the axial directiondue to the twisting direction thereof, by which the projection endsurface 17a1 of the male coupling shaft 17 is abutted to the recessbottom surface 18a1 (or, the male shaft end surface 17b is abutted tothe end surface 18b of the female shaft).

Since the position of the process cartridge B is constant in thedirection of the coupling shaft in the main assembly A of the imageforming apparatus during the driving operation, the vibration of theprocess cartridge can be suppressed.

In this example, the cross-sectional configurations of the projection17a of the coupling shaft and the recess 18a are substantiallyrectangular configurations, but another polygonal prism shape is usableif the engagement is established when the coupling recess is rotated.

When the process cartridge B is demounted from the main assembly, themotor 30 may be rotated in the opposite direction, the couplingengagement is automatically released due to the thrust between the gear33 and the helical gear 34. In this case, there is no need of using thecoupling release mechanism as in embodiment 1.

Embodiment 6

Referring to FIG. 23, the description will be made as to a furtherembodiment. The embodiment of FIG. 23 is different from embodiment 1 inthat the gear is not provided on the drum flange 16.

The coupling structure shown in FIGS. 23(a) and (b), is such that themain assembly side coupling means is of a female coupling shaft 17 ofpolyacetal (POM), and the coupling means of the cartridge sideengageable therewith is of a male coupling shaft 18 of POM. Acylindrical wall portion 24 concentric with the photosensitive drum 7 isformed integrally with the flange 16 is provided around the malecoupling shaft 18. FIG. 23(b) are views as seen in the directions D andE of FIG. 23(a).

By the provision of a wall portion 24 having substantially the sameheight as the projection 18a around the male shaft 18, the projection18a is not projected out beyond the cartridge frame, so that the damageof the end portion f the projection 18a can be prevented.

The cylindrical wall portion 24 may also function as a guide forfacilitating the mounting of the process cartridge B to the imageforming apparatus A (FIG. 6, guide c), as described in the foregoing.

Embodiment 7

Referring to FIGS. 24 and 25, another embodiment will be described. Inthis embodiment, as contrasted to the above-described embodiment, thedrum flange 116 of the photosensitive drum 7 is provided with a femaleshaft 117, and the large diameter gear 121 of the main assembly 13 ofthe apparatus is provided with a male shaft 118. The rotation accuracycan be improved, with this structure, too.

As shown in FIG. 24, the substantially positive triangular prism of theprojection 118a of the male coupling shaft 118 is twisted in therotation direction, and the recess 117a of the female coupling shaft 117is twisted correspondingly in the rotation direction. A seat 117b isprovided at the end surface of the female coupling shaft 117.

By the twisting of the engaging portion in the rotation direction, themale coupling shaft 118 pulls the female shaft 117 until it is abuttedto the seat 117b when the male coupling shaft 118 is rotated in thedirection c for image formation while they are engaged. As a result, thecombination therebetween is further assured.

When the process cartridge B is demounted from the main assembly 13,motor 119 may be rotated in the opposite direction indicated by arrow d,by which the engagement of the coupling is automatically released by thethrust produced by the meshing between the pinion gear 120 having thehelical teeth and the transmission gear 121, as shown in FIG. 25.

In this example, if the tolerable transmission torque of the femaleshaft 117 is smaller than the tolerable transmission torque of the maleshaft 118, the damage of the male shaft 118 can be prevented.

For example, the female coupling shaft provided in the cartridge is madeof polyacetal (POM), and the male coupling shaft constituted in the mainassembly is made of zinc die-cast. By doing so, even if an abnormaltorque is produced, the damage of the male shaft is prevented since thetolerable transmission torque of the male coupling shaft of the mainassembly side is large.

This embodiment is the same as embodiment 1 except that the female shaftis provided in the drum flange, and the male shaft is provided in themain assembly. Therefore, the embodiments of the electrophotographicimage forming apparatus, the process cartridge, the drive transmissionpart and the electrophotographic photosensitive drum are the same asthose of embodiment 1, except that the male shaft of the drum flange isreplaced with the female shaft, and the female shaft of the gear of themain assembly is replaced with the male shaft, and therefore, thedescription of such embodiments are omitted for simplicity.

However, the process cartridge will be described briefly. It is aprocess cartridge B which is detachably mountable to a main assembly 13of an electrophotographic image forming apparatus A. Theelectrophotographic image forming apparatus A comprises a motor 30(119), the main assembly helical gear 34 (121) for receiving the drivingforce from the motor 30 (119), and a twisted triangular prism projection118a integrally rotatable with the main assembly helical gear providedat the main assembly helical gear of the main assembly helical gear 34(121). The electrophotographic image forming apparatus A operates toform an image on the recording medium. The process cartridge B comprisescartridge frames 12a, 12b and 12c, the electrophotographicphotosensitive drum 7 (107), the charging roller 8 for charging theelectrophotographic photosensitive drum 7 (107), the cleaning blade 11afor removing the residual toner from the electrophotographicphotosensitive drum 7 (107), the developing roller 10d for developingthe latent image formed on the electrophotographic photosensitive drum 7(107), and a twisted triangular hole 117a engageable with the projection118a provided at a longitudinal end of the electrophotographicphotosensitive drum 7 (107). The process cartridge B is mounted to themain assembly, and when the main assembly helical gear 34 (121) isrotated with the hole 117a engaged with the projection 118a, therotational force is transmitted from the main assembly helical gear 34(121) to the drum 7 (121) while the hole 117a is kept pulled toward theprojection 118a. The hole 117a is formed as a recess at a leading edgeof the shaft portion 17 (117) provided at the central portion of thedrum helical gear 16a (116a). The drum helical gear 16a (116a) functionsto transmit the rotation force to the developing roller 10d. The shaftportion 17 (117) functions to rotatably support the electrophotographicphotosensitive drum 7 (107) on the cartridge frame 112c. The drumhelical gear 16 (116a) of the hole 117 and the shaft portion 17 (117)are integrally formed from resin material. Outer diameter D1 of theelectrophotographic photosensitive drum 7 (107), the outer diameter F ofthe shaft portion, and the diameter C of the circumscribed circle of thehole configuration 117a, satisfy D1>F>C.

The outer diameter F of the shaft portion 17 (117), the diameter C ofthe circumscribed circle of the hole configuration, the dedendumdiameter G of the gear 16a of the electrophotographic photosensitivedrum 7, and the inner diameter D2 of the electrophotographicphotosensitive drum 7, satisfy G>D2 and G>F>C. The outer diameter D1 ofthe electrophotographic photosensitive drum 7 (107), and the dedendumcircle diameter L of the main assembly gear 34 (121), L is preferablynot less than approx. 1.0 times D1 and not more than 5.0 times D1. Themodule of the main assembly gear 34 (121) is approx. 0.4-0.7. Thededendum diameter L of the main assembly gear of the device is approx.30 mm-150 mm, and the number of teeth of the main assembly gear 34 isapprox. 40 teeth-400 teeth.

In this example, the direction of twisting of the projection 118a asseen from the photosensitive drum 7 (107) is the same as the rotationdirection of the photosensitive drum 7 (107) in the direction from thebase portion of the projection 118a toward the end, and that of the hole117a is the same in the direction from the inlet of the hole 117a towardthe inside thereof. The twisting direction of the drum flange 16a (116a)is opposite from the twisting direction of the hole 117a.

Embodiment 8

In embodiment 1, when the cover 14 is opened, the rod 37 and the cam 35are operated in interrelation therewith to release the engagementbetween the coupling projection 17a and the recess 18a. The couplingrelease structure may be as disclosed in FIGS. 26 and 27.

The openable cover 14 is provided with an arcuate releasing member 140at the center of the shaft 14a, as shown in FIG. 26(a), and the leadingedge of the releasing member 140 is formed into a cam portion 140ahaving a gradually increasing thickness, as shown in FIG. 26(b). Asshown in FIGS. 27(a) and (b), when the cover 114 is opened to demountthe process cartridge B, the cam portion 140a enters the space betweenthe wall portion 141 and the gear 34 integral with the female shaft 18to push the side surface of the gear 34 out in the direction indicatedby arrow b in FIG. 27. By this, the female shaft 18 is retracted fromthe wall portion 141 so that the engagement with the male coupling shaft17 of the photosensitive drum 7 is released to permit smooth demountingof the process cartridge B.

The member for mounting the releasing member 140 is not limited to theopenable cover 14 if it is a member operated when the process cartridgeB is mounted or demounted. When the drive transmission gear 34 is ahelical gear, the releasing member 140 is not inevitable, and thecoupling release is possible by the thrust produced by the helical gear.

Further Embodiment

In the first embodiment, the coupling of the photosensitive drum isconstituted as a male shaft 17, and the coupling of the main assembly isconstituted as a female shaft 18, but the female shaft and the maleshaft may be exchanged. In such a case, the same advantageous effects inthe rotation accuracy of the photosensitive drum can be provided (FIGS.23 and 24). In this example, if the tolerable transmission torque of thefemale shaft of the photosensitive drum is smaller than the tolerabletransmission torque of the male shaft of the main assembly, the damageof the male shaft of the main assembly can be prevented.

For example, the female coupling shaft provided in the cartridge is madeof polyacetal (POM), and the male coupling shaft constituted in the mainassembly is made of zinc die-cast. By doing so, even if an abnormaltorque is produced, the damage of the male shaft is prevented since thetolerable transmission torque of the male coupling shaft of the mainassembly side is large.

In the above-described embodiment, if a taper is formed at the endportion of the projection 17a or at the inlet portion of the recess 18aor at the both, combination between the projection 17a and the recess18a is smoother.

In the foregoing, the process cartridge has been described as acartridge for monochromatic image formation, but it is applicable to acartridge for forming a multi-color image (two color, three color orfull-color image, for example) if a plurality of developing means areused.

As for the developing method, any known methods such as a two-componentmagnetic brush developing method, a cascade developing method, atouch-down developing method, cloud developing method or the like may beused.

As for the electrophotographic photosensitive member, usable onesinclude amorphous silicon, amorphous selenium, zinc oxide, titaniumoxide, organic photoconductor (OPC) and the like. As for methods formountings photosensitive material, a photoconductor is evaporated orpainted or applied on a cylinder of aluminum alloy or the like.

As for the charging means, a so-called contact type charging method isused in the foregoing examples. However, another method such as coronacharging is usable, in which a tungsten wire is enclosed by metal shieldof aluminum or the like at three side of the wire, and positive ornegative ions are produced by applying a high voltage to the tungstenwire, and the surface of the photosensitive drum is uniformly charged bymoving positive or negative ions to the surface.

As for the charging means, blade type (charging blade), pad type, blocktype, rod type, wire type or the like is usable in addition to theroller type.

As for the cleaning means for removing residual toner from thephotosensitive drum, fur brush, magnetic brush or the like is usable, aswell as the cleaning blade.

The process cartridge may contain a photosensitive member and at leastone process means. The process cartridge may contain a photosensitivedrum and charging means and is made detachably mountable to a mainassembly of the apparatus. The process cartridge may contain aphotosensitive drum and developing means and is made detachablymountable to a main assembly of the apparatus. The process cartridge maycontain a photosensitive drum and cleaning means and is made detachablymountable to a main assembly of the apparatus. The process cartridge maycontain a photosensitive drum and at least two process means.

The process cartridge may contain a photosensitive drum and chargingmeans, developing means or cleaning means, and is made detachablymountable to a main assembly of the apparatus. The process cartridge maycontain a photosensitive drum and at least one of charging means,developing means and cleaning means, and is made detachably mountable toa main assembly of the apparatus. The process cartridge may contain aphotosensitive drum and at least developing means, and is madedetachably mountable to a main assembly of the apparatus. Since theprocess cartridge is detachably mountable to the main assembly of theimage forming apparatus by the user, this means that the maintenance ofthe apparatus using the process cartridge can be performed by the userby exchanging the process cartridge.

The present invention is applicable to a non-cartridge type imageforming apparatus wherein the photosensitive drum, the developing meansor the like is directly mounted to the main assembly of the apparatus.

In the foregoing, the description has been made as to a laser beamprinter as an exemplary image forming apparatus, but the presentinvention is applicable to an electrophotographic copying machine,facsimile machine, word processor or another image forming machine.

As described in the foregoing, according to the present invention, therotation accuracy of the driving transmission is improved, so therotation accuracy of the electrophotographic photosensitive drum hasbeen improved.

Additionally, the driving force can be assuredly transmitted from themain assembly to the electrophotographic photosensitive drum.

Furthermore, when the driving force is transmitted (during an imageforming operation), the rotation center of the coupling of the mainassembly of the apparatus and the coupling of the electrophotographicphotosensitive drum can be substantially aligned.

Further additionally, when the driving force is transmitted (during theimage forming operation), the electrophotographic photosensitive drum isattracted toward the main assembly side, so that the positional accuracyof the photosensitive member and therefore the process cartridgerelative to the main assembly is improved.

Further additionally, when the driving transmission is not carried out(when the image is not formed), the drive transmission coupled state isreleased, so that the operativity in demounting of the process cartridgeis improved. Further additionally, the diameter of the diameter of thecoupling portion is small.

While the invention has been described with reference to the structuresdisclosed herein, it is not confined to the details set forth and thisapplication is intended to cover such modifications or changes as maycome within the purposes of the improvements or the scope of thefollowing claims.

What is claimed is:
 1. An electrophotographic image forming apparatusfor forming an image on a recording material, comprising:anelectrophotographic photosensitive drum; charging means for chargingsaid photosensitive drum; developing means for developing a latent imageformed on said photosensitive drum into a toner image; transfer meansfor transferring the toner image onto the recording material; fixingmeans for fixing the toner image on the recording material; a motor; adriving rotatable member for receiving a driving force from said motor;a twisted hole substantially coaxial with said driving rotatable member,said hole having a polygonal cross-section; a twisted prism projectionprovided at a longitudinal end of said photosensitive drum, wherein whensaid driving rotatable member rotates with said hole and projectionengaged with each other, a rotational driving force is transmitted fromsaid driving rotatable member to said photosensitive drum throughengagement between said hole and said projection with said projectionbeing pulled into said hole; and moving means for imparting relativemovement between said hole and said projection in a longitudinaldirection of said photosensitive drum.
 2. An apparatus according toclaim 1, wherein said hole is formed in an end of a first columnprojected from a rotational axis of said driving rotatable member, andsaid projection is projected from an end of a shaft projected outwardlyin a rotational direction from said photosensitive drum.
 3. An apparatusaccording to claim 2, wherein an outer diameter D1 of saidphotosensitive drum, an outer diameter F of said shaft and a diameter Cof a circumscribed circle of said projection, satisfy:D1>F≧C.
 4. Anapparatus according to claim 1 or 2, further comprising a drum gear,wherein said developing means includes a developing roller, and whereinsaid projection is provided at a drum gear side of said photosensitivedrum, and wherein said drum gear functions to transmit the driving forceto said developing roller.
 5. An apparatus according to claim 4, whereinsaid developing means includes a developing roller, and wherein saiddriving rotatable member and drum gear are helical gears, said helicalgears transmitting driving force to said developing roller.
 6. Anapparatus according to claim 1, further comprising a circular or arcuatewall extending around said projection, said wall functioning as a guidefor engagement between said hole and projection.
 7. An apparatusaccording to claim 1 or 2, wherein an outer diameter F of said shaft, adiameter C of a circumscribed circle of said projection, a dedendumdiameter G of a drum gear of said photosensitive drum and an innerdiameter of said photosensitive drum D2, satisfy:G>D2, and G>F≧C.
 8. Anapparatus according to claim 1 or 6, wherein an outer diameter D1 ofsaid photosensitive drum and dedendum diameter L of said drivingrotatable member satisfy: 1.0×D1≦L≦5.0×D1, approximately.
 9. Anapparatus according to claim 1 or 6, wherein said driving rotatablemember has a module of approximately 0.4-0.7 and has a dedendum diameterL of approximately 30-150 mm, and further has 40-400 teeth.
 10. Anapparatus according to claim 1 or 6, wherein said hole has asubstantially triangular cross-section, and said projection has asubstantially triangular cross-section, and wherein corners of thetriangular shapes are beveled.
 11. An apparatus according to claim 1,wherein said photosensitive drum, said charging means and saiddeveloping means are contained in a process cartridge which isdetachably mountable to said apparatus.
 12. An apparatus according toclaim 11, further comprising an openable cover for permitting mountingand demounting of said process cartridge relative to a main assembly ofsaid apparatus, and said moving means are for moving said hole away fromsaid projection in interrelation with opening of said cover, and are formoving said hole toward said projection in interrelation with closing ofsaid cover; and means for feeding the recording material.
 13. A processcartridge detachably mountable to a main assembly of an image formingapparatus, wherein said main assembly includes a motor, a drivingrotatable member for receiving a driving force from said motor, and atwisted hole having a polygonal cross-section and formed substantiallycoaxial with said driving rotatable member, said process cartridgecomprising:an electrophotographic photosensitive drum; process meansactable on said photosensitive drum; and a twisted polygonal prismprojection provided at a longitudinal end of said photosensitive drum,wherein when said driving rotatable member rotates with said hole andprojection engaged with each other, a rotational driving force istransmitted from said driving rotatable member to said photosensitivedrum through engagement between said hole and said projection with saidprojection being pulled into said hole.
 14. A process cartridgeaccording to claim 13, wherein said projection is projected from an endof a shaft projected outwardly in a rotational axis direction from saidphotosensitive drum and said shaft functions to rotatably support saidphotosensitive drum in a cartridge frame.
 15. A process cartridgeaccording to claim 14, wherein said process means includes a developingroller, wherein said shaft is substantially coaxial with a helical gear,and at a side opposite from said shaft, there is provided an engagingportion for engagement with an inner surface of said photosensitivedrum, and wherein said projection, helical gear, engaging portion andshaft are of integrally molded resin material, and the helical geartransmits driving force to said developing roller.
 16. A processcartridge according to claims 13 or 15, further comprising a circular orarcuate wall extending around said projection, said wall functions as aguide for engagement between said hole and projection.
 17. A processcartridge according to claim 15, wherein an outer diameter D1 of saidphotosensitive drum, an outer diameter F of said shaft, and a diameter Cof a circumscribed circle of said projection, satisfy:D1>F≧C.
 18. Aprocess cartridge according to claim 13 or 15, wherein said hole has asubstantially triangular cross-section, and said projection has asubstantially triangular cross-section, and wherein corners of thetriangular shapes are beveled.
 19. A process cartridge according toclaim 13, further comprising a portion to be urged by a part of the mainassembly by a spring and a portion to be contacted to a fixed portion ofthe main assembly, when said process cartridge is mounted to the mainassembly.
 20. A process cartridge according to claim 13, wherein saidprocess means includes at least one of charging means, developing meansand cleaning means as a unit.
 21. An electrophotographic image formingapparatus, for forming an image on a recording material, to which aprocess cartridge is detachably mountable, said apparatus comprising:amotor; a driving rotatable member for receiving a driving force fromsaid motor; a twisted hole substantially coaxial with said drivingrotatable member, said hole having a polygonal cross-section; means formounting a process cartridge, the process cartridge including:anelectrophotographic photosensitive drum; process means actable on saidphotosensitive drum; and a twisted polygonal prism projection providedat a longitudinal end of said photosensitive drum, wherein when saiddriving rotatable member rotates with said hole and projection engagedwith each other, a rotational driving force is transmitted from saiddriving rotatable member to said photosensitive drum through engagementbetween said hole and said projection with said projection being pulledinto said hole; moving means for imparting relative movement betweensaid hole and said projection in a longitudinal direction of saidphotosensitive drum; and means for feeding the recording material. 22.An apparatus according to claim 21, wherein a shaft of saidphotosensitive drum is substantially coaxial with a helical gear, and ata side opposite from said shaft, there is provided an engaging portionfor engagement with an inner surface of said photosensitive drum,wherein said projection, helical gear, engaging portion and shaft aremade of integrally molded resin material, and said helical geartransmits driving force to a developing roller as said process means.23. An apparatus according to claim 21, wherein said process cartridgefurther comprises a portion to be urged by a part of a main assembly ofsaid apparatus by a spring and a portion to be contacted to a fixedportion of the main assembly, when said process cartridge is mounted tothe main assembly.
 24. An apparatus according to claim 21, wherein saidprocess means includes at least one of charging means, developing meansand cleaning means as a unit.
 25. An apparatus according to claim 24,wherein said process cartridge further includes a drum gear, whereinsaid driving rotatable member and drum gear are helical gears, andwherein said helical gears transmit a driving force to a developingroller as said process means.
 26. An apparatus according to claim 21,wherein a shaft is projected outwardly in a rotational axis directionfrom said photosensitive drum, and said shaft functions to rotatablysupport said photosensitive drum in a cartridge frame, and wherein anouter diameter F of the shaft, a diameter C of a circumscribed circle ofsaid projection, a dedendum diameter G of a gear of said photosensitivedrum and an inner diameter D2 of said photosensitive drum, satisfy:G>D2,and G>F≧C.
 27. An apparatus according to claim 21, wherein an outerdiameter D1 of said photosensitive drum and dedendum diameter L of saiddriving rotatable member satisfy:1.0×D1≦L≦5.0×D1, approximately.
 28. Anapparatus according to claim 21, wherein said driving rotatable memberhas a module of approximately 0.4-0.7 and has a dedendum diameter L ofapproximately 30-150 mm, and further has 40-400 teeth.
 29. An apparatusaccording to claim 21, further comprising an openable cover forpermitting mounting and demounting of said process cartridge relative toa main assembly of said apparatus, and said moving means are for movingsaid hole away from said projection in interrelation with opening ofsaid cover, and are for moving said hole toward said projection ininterrelation with closing of said cover.
 30. A process cartridgedetachably mountable to a main assembly of an image forming apparatus,wherein said main assembly includes a motor, a driving rotatable memberfor receiving driving force from said motor and a twisted holesubstantially coaxial with said driving rotatable member, said holehaving a substantially triangular cross-section, said process cartridgecomprising:a cartridge frame; an electrophotographic photosensitivedrum; a developing roller for developing a latent image formed on saidphotosensitive drum; and a twisted substantially triangular prismprojection provided at a longitudinal end of said photosensitive drum,wherein when said driving rotatable member rotates with said hole andprojection engaged with each other, a rotational driving force istransmitted from said driving rotatable member to said photosensitivedrum through engagement between said hole and said projection with saidprojection being pulled into said hole; and wherein said projection isprovided at an end of a shaft substantially coaxial with a drum helicalgear for transmitting rotational force to said developing roller, andwherein said shaft functions to rotatably support said photosensitivedrum in said cartridge frame.
 31. A process cartridge according to claim30, wherein at a side of said photosensitive drum opposite from saidshaft, there is provided an engaging portion for engagement with aninner surface of said photosensitive drum, wherein said projection, drumhelical gear, engaging portion and shaft are made of integrally moldedresin material, and wherein a supporting shaft is projected outwardly ina rotational axis direction from said photosensitive drum, and saidsupporting shaft functions to rotatably support said photosensitive drumin said cartridge frame.
 32. A process cartridge according to claim 30,further comprising a circular or arcuate wall extending around saidprojection, wherein said wall functions as a guide for engagementbetween said hole and projection.
 33. A process cartridge according toclaim 30 or 31, wherein an outer diameter F of said shaft, a diameter Cof a circumscribed circle of said projection, a dedendum diameter G ofsaid drum helical gear and an inner diameter D2 of said photosensitivedrum, satisfy:G>D2, and G>F≧C.
 34. A process cartridge according toclaim 30, wherein corners of said projection are beveled.
 35. A processcartridge according to claim 30, further comprising a portion to beurged by a part of the main assembly by a spring and a portion to becontacted to a fixed portion of the main assembly, when said processcartridge is mounted to the main assembly.
 36. A process cartridgeaccording to claim 30, wherein said process cartridge further comprisesat least one of a changing roller and a cleaning blade.
 37. Anelectrophotographic image forming apparatus, for forming an image on arecording material, having a main assembly to which a process cartridgeis detachably mountable, said apparatus comprising:a motor; a drivingrotatable member for receiving a driving force from said motor; atwisted hole formed substantially coaxial with said driving rotatablemember, said hole having a substantially triangular cross-section; meansfor mounting a process cartridge, the process cartridge including:acartridge frame; an electrophotographic photosensitive drum; adeveloping roller for developing a latent image formed on saidphotosensitive drum; and a twisted substantially triangular prismprojection provided at a longitudinal end of said photosensitive drum,wherein when said driving rotatable member rotates with said hole andprojection engaged with each other, a rotational driving force istransmitted from said driving rotatable member to said photosensitivedrum through engagement between said hole and said projection with saidprojection being pulled into said hole, wherein said projection isprovided at an end of a shaft substantially coaxial with a drum helicalgear for transmitting rotational force to said developing roller, andwherein said shaft functions to rotatably support said photosensitivedrum in said cartridge frame; moving means for imparting relativemovement between said hole and said projection in a longitudinaldirection of said photosensitive drum; and means for feeding therecording material.
 38. An apparatus according to claim 37, wherein at aside opposite from said shaft, there is provided an engaging portion forengagement with an inner surface of said photosensitive drum, andwherein said projection, drum helical gear, engaging portion and shaftare made of integrally molded resin material.
 39. An apparatus accordingto claim 37, wherein said process cartridge further comprises a portionto be urged by a part of the main assembly by a spring and a portion tobe contacted to a fixed portion of the main assembly, when said processcartridge is mounted to the main assembly.
 40. An apparatus according toclaim 37, wherein said process cartridge further comprises at least oneof charging roller and cleaning blade.
 41. An apparatus according toclaim 37, wherein an outer diameter F of said shaft, a diameter C of acircumscribed circle of said projection, a dedendum diameter G of saiddrum helical gear and an inner diameter D2 of said photosensitive drum,satisfy:G>D2, and G>F≧C.
 42. An apparatus according to claim 37, whereinan outer diameter D1 of said photosensitive drum and dedendum diameter Lof said driving rotatable member satisfy:1.0×D1≦L≦5.0×D1, approximately.43. An apparatus according to claim 37, wherein said driving rotatablemember has a module of approximately 0.4-0.7 and has a dedendum diameterL of approximately 30-150 mm, and further has 40-400 teeth.
 44. Anapparatus according to claim 37, further comprising an openable coverfor permitting mounting and demounting of said process cartridgerelative to said main assembly, wherein said moving means are for movingsaid hole away from said projection in interrelation with opening ofsaid cover, and are for moving said hole toward said projection ininterrelation with closing of said cover.
 45. A process cartridgedetachably mountable to a main assembly of an image forming apparatus,wherein said main assembly includes a motor, a main assembly sidehelical gear for receiving driving force from said motor and a twistedhole substantially coaxial with said main assembly side helical gear,said hole having a substantially triangular cross-section, said processcartridge comprising:a cartridge frame; an electrophotographicphotosensitive drum; a charging roller for charging said photosensitivedrum; a developing roller for developing a latent image formed on saidphotosensitive drum; a cleaning blade for removing residual toner fromsaid photosensitive drum; and a twisted substantially triangular prismprojection provided at a longitudinal end of said photosensitive drum,wherein when said main assembly side helical gear rotates with said holeand projection engaged with each other, rotational driving force istransmitted from said main assembly side helical gear to saidphotosensitive drum through engagement between said hole and saidprojection with said projection being pulled into said hole; and whereinsaid projection is provided at an end of a shaft substantially coaxialwith a drum helical gear for transmitting rotational force to saiddeveloping roller, and wherein said shaft functions to rotatably supportsaid photosensitive drum in said cartridge frame, and wherein saidprojection, drum helical gear and shaft are made of integrally moldedresin material, and an outer diameter D1 of said photosensitive drum, anouter diameter F of said shaft and a diameter C of a circumscribedcircle of said substantially triangular prism projection,satisfy:D1>F≧C.
 46. A process cartridge according to claim 45, whereinat a side opposite from said shaft, there is provided an engagingportion for engagement with an inner surface of said photosensitivedrum, wherein said projection, drum helical gear, engaging portion andshaft are made of integrally molded resin material.
 47. A processcartridge according to claim 45, further comprising a circular orarcuate wall extending around said projection, wherein said wallfunctions as a guide for engagement between said hole and projection.48. A process cartridge according to claim 45, wherein corners of saidprojection are beveled.
 49. A process cartridge according to claim 45,further comprising a portion to be urged by a part of the main assemblyby a spring and a portion to be contacted to a fixed portion of the mainassembly, when said process cartridge is mounted to the main assembly.50. An electrophotographic image forming apparatus, for forming an imageon a recording material, to which a process cartridge is detachablymountable, said apparatus comprising:a motor; a main assembly sidehelical gear for receiving driving force from said motor; a twisted holesubstantially coaxial with said main assembly side helical gear, saidhole having a substantially triangular cross-section, said hole beingformed in an end of a circular column projected from a substantiallycentral portion of said main assembly side helical gear; means formounting a process cartridge, the process cartridge including:acartridge frame; an electrophotographic photosensitive drum; a chargingroller for charging said photosensitive drum; a developing roller fordeveloping a latent image formed on said photosensitive drum; a cleaningblade for removing residual toner from said photosensitive drum; and atwisted substantially triangular prism projection provided at alongitudinal end of said photosensitive drum, wherein when said mainassembly side helical gear rotates with said hole and projection engagedwith each other, rotational driving force is transmitted from said mainassembly side helical gear to said photosensitive drum throughengagement between said hole and said projection with said projectionbeing pulled into said hole; and wherein said projection is provided atan end of a shaft substantially coaxial with a drum helical gear fortransmitting rotational force to said developing roller, and whereinsaid shaft functions to rotatably support said photosensitive drum insaid cartridge frame, and wherein said projection, drum helical gear andshaft are made of integrally molded resin material, and an outerdiameter D1 of said photosensitive drum, an outer diameter F of saidshaft and a diameter C of a circumscribed circle of said substantiallytriangular prism projection, satisfy D1>F≧C; an openable cover forpermitting mounting and demounting of said process cartridge relative tosaid main assembly; moving means for moving said hole away from saidprojection in interrelation with opening of said cover, and for movingsaid hole toward said projection in interrelation with closing of saidcover; and means for feeding the recording material, wherein a dedendumdiameter G of said drum helical gear and an inner diameter D2 of saidphotosensitive drum, satisfy:G>D2, and G>F≧C.
 51. An apparatus accordingto claim 50, wherein said main assembly side helical gear has a moduleof approximately 0.4-0.7 and has a dedendum diameter L of approximately30-150 mm, and further has 40-400 teeth.
 52. A drive transmission partfor transmitting a driving force to an electrophotographicphotosensitive drum and a developing roller for developing a latentimage formed on said photosensitive drum, which are contained in aprocess cartridge detachably mountable to a main assembly of an imageforming apparatus for forming an image on a recording material, saidmain assembly including a motor, a driving rotatable member forreceiving a driving force from said motor, and a twisted holesubstantially coaxial with said driving rotatable member, said holehaving a polygonal cross-section, said drive transmission partcomprising:a transmission part gear for transmitting a driving forcefrom said main assembly to said developing roller when said processcartridge is mounted to the main assembly; a shaft substantially coaxialwith said transmission part gear; and a twisted polygonal prismprojection provided at an end of said shaft, wherein said projectionreceives a driving force from the main assembly through engagementbetween said hole and projection, wherein the driving force istransmitted to said photosensitive drum through said shaft, and istransmitted to said developing roller through said transmission partgear.
 53. A part according to claim 52, wherein an outer diameter D1 ofsaid photosensitive drum, an outer diameter F of said shaft and adiameter C of a circumscribed circle of said projection, satisfy:D1>F≧C.54. A part according to claim 52, wherein said projection, transmissionpart gear, and shaft are made of integrally molded resin material.
 55. Apart according to claim 54, wherein said resin material is polyacetalresin, polycarbonate resin, polyamide resin, orpolyethyleneterephthalate resin.
 56. A drive transmission part fortransmitting driving force to an electrophotographic photosensitive drumand a developing roller for developing a latent image formed on saidphotosensitive drum, which are contained in a process cartridgedetachably mountable to a main assembly of an image forming apparatusfor forming an image on a recording material, said main assemblyincluding a motor, a main assembly side gear for receiving driving forcefrom said motor, and a twisted hole substantially coaxial with said mainassembly side gear, said hole having a substantially triangularcross-section, said drive transmission part comprising:a helical gearfor transmitting driving force from said main assembly to saiddeveloping roller when said process cartridge is mounted to the mainassembly; a shaft substantially coaxial with said helical gear; and atwisted substantially triangular prism projection provided at an end ofsaid shaft, wherein when said main assembly side gear rotates with saidhole and projection engaged with each other, rotational driving force istransmitted from said main assembly side gear to said photosensitivedrum through engagement between said hole and said projection with saidprojection being pulled into said hole, and the driving force istransmitted to said photosensitive drum through said shaft and istransmitted to said developing roller through said helical gear, whereinsaid projection, helical gear and shaft are made of integrally moldedresin material, and an outer diameter D1 of said photosensitive drum, anouter diameter F of said shaft and a diameter C of a circumscribedcircle of said projection, satisfy: D1>F≧C.
 57. A photosensitive drum,which is contained in a process cartridge detachably mountable to a mainassembly of an image forming apparatus for forming an image on arecording material, said main assembly including a motor, a drivingrotatable member for receiving a driving force from said motor, and atwisted hole substantially coaxial with said driving rotatable member,said hole having a polygonal cross-section, said photosensitive drumcomprising:a cylinder having a photosensitive layer thereon; and a drivetransmission member mounted to an end of said cylinder, said drivetransmission member including:a drum gear for transmitting a drivingforce from said main assembly to a developing roller provided in theprocess cartridge when the process cartridge is mounted to the mainassembly; a shaft substantially coaxial with said drum gear; and atwisted polygonal prism projection provided at an end of said shaft,wherein said projection receives a driving force from the main assemblythrough engagement between said hole and projection, wherein the drivingforce is transmitted to said photosensitive drum through the shaft, andis transmitted to said developing roller through said drum gear.
 58. Aphotosensitive drum according to claim 57, wherein an outer diameter D1of said photosensitive drum, an outer diameter F of said shaft and adiameter C of a circumscribed circle of said projection, satisfy:D1>F≧C.59. A photosensitive drum according to claim 57, wherein saidprojection, drum gear and shaft are made of integrally molded resinmaterial.
 60. A photosensitive drum according to claim 59, wherein saidresin material is polyacetal resin, polycarbonate resin, polyamideresin, or polyethyleneterephthalate resin.
 61. A photosensitive drumaccording to claim 57, wherein a spur gear is mounted to another end ofsaid cylinder, and wherein said spur gear functions to transmit adriving force for rotating an image transfer roller.
 62. Aphotosensitive drum, which is contained in a process cartridgedetachably mountable to a main assembly of an image forming apparatusfor forming an image on a recording material, said main assemblyincluding a motor, a main assembly side gear for receiving driving forcefrom said motor, and a twisted hole substantially coaxial with said mainassembly side gear, said hole having a substantially triangularcross-section, said photosensitive drum comprising:a cylinder having aphotosensitive layer thereon; and a drive transmission member mounted toan end of said cylinder, said transmission member including:a helicalgear for transmitting driving force from said main assembly to adeveloping roller provided in said process cartridge when said processcartridge is mounted to the main assembly; a shaft substantially coaxialwith said helical gear; and a twisted substantially triangular prismprojection provided at an end of said shaft, wherein when said mainassembly side gear rotates with said hole and projection engaged witheach other, rotational driving force is transmitted from said mainassembly side gear to said photosensitive drum through engagementbetween said hole and said projection with said projection being pulledinto said hole, and the driving force is transmitted to saidphotosensitive drum through said shaft and is transmitted to saiddeveloping roller through said helical gear, wherein said projection,helical gear and shaft are made of integrally molded resin material, andan outer diameter D1 of said photosensitive drum, an outer diameter F ofsaid shaft and a diameter C of a circumscribed circle of saidprojection, satisfy:D1>F≧C, and wherein a spur gear is provided, atanother end of said cylinder, for transmitting the driving force forrotating an image transfer roller in the main assembly when said processcartridge is mounted to the main assembly.
 63. An electrophotographicimage forming apparatus for forming an image on a recording material,said apparatus comprising:an electrophotographic photosensitive drum;charging means for charging said photosensitive drum; developing meansfor developing a latent image formed on said photosensitive drum into atoner image; transfer means for transferring the toner image onto therecording material; fixing means for fixing the toner image on therecording material; a motor; a driving rotatable member for receiving adriving force from said motor; a twisted prism projection substantiallycoaxial with said driving rotatable member, said projection having apolygonal cross-section; a twisted polygonal hole having a polygonalcross-section and provided at a longitudinal end of said photosensitivedrum, wherein when said driving rotatable member rotates with saidprojection and hole engaged with each other, a rotational driving forceis transmitted from said driving rotatable member to said photosensitivedrum through engagement between said projection and said hole with saidhole being pulled into said projection; and moving means for impartingrelative movement between said projection and said hole in alongitudinal direction of said photosensitive drum.
 64. An apparatusaccording to claim 63, wherein said projection is formed in an end of afirst column projected in a rotational axis direction from said drivingrotatable member, and said hole is provided at an end of a shaftprojected outwardly in a rotational axis direction from saidphotosensitive drum.
 65. An apparatus according to claim 64, furthercomprising a drum gear disposed on said photosensitive drum, whereinsaid hole is provided at a drum gear side of said photosensitive drum,and said drum gear functions to transmit the driving force to adeveloping roller as said developing means.
 66. An apparatus accordingto claim 65, wherein said driving rotatable member and drum gear arehelical gears.
 67. An apparatus according to claim 65, wherein an outerdiameter F of said shaft, a diameter C of a circumscribed circle of saidprojection, a dedendum diameter G of the drum gear and an inner diameterD2 of said photosensitive drum, satisfy:G>D2, and G>F≧C.
 68. Anapparatus according to claim 64, wherein an outer diameter D1 of saidphotosensitive drum, an outer diameter F of said shaft and a diameter Cof a circumscribed circle of said projection, satisfy:D1>F≧C.
 69. Anapparatus according to claim 63, further comprising a circular orarcuate wall extending around said hole, said wall functioning as aguide for engagement between said projection and hole.
 70. An apparatusaccording to claim 63 or 69, wherein an outer diameter D1 of saidphotosensitive drum and dedendum diameter L of said driving rotatablemember satisfy:1.0×D1≦L≦5.0×D1, approximately.
 71. An apparatusaccording to claim 63 or 69, wherein said driving rotatable member has amodule of approximately 0.4-0.7 and has a dedendum diameter L ofapproximately 30-150 mm, and further has 40-400 teeth.
 72. An apparatusaccording to claim 63 or 68, wherein said projection has a substantiallytriangular cross-section, and said hole has a substantially triangularcross-section, and wherein corners of triangular shapes are beveled. 73.An apparatus according to claim 63, wherein said photosensitive drum andat least one of said charging means and said developing means arecontained in a cartridge which is detachable mountable.
 74. An apparatusaccording to claim 73, further comprising an openable cover forpermitting mounting and demounting of said process cartridge relative toa main assembly of said image forming apparatus, wherein said movingmeans are for moving said projection away from said hole ininterrelation with opening of said cover, and are for moving saidprojection toward said hole in interrelation with closing of said cover.75. A process cartridge detachably mountable to a main assembly of animage forming apparatus, wherein said main assembly includes a motor, adriving rotatable member for receiving a driving force from said motorand a twisted prism projection substantially coaxial with said drivingrotatable member, said projection having a polygonal cross-section, saidprocess cartridge comprising:an electrophotographic photosensitive drum;process means actable on said photosensitive drum; and a twistedpolygonal hole having a polygonal cross-section and provided at alongitudinal end of said photosensitive drum, wherein when said drivingrotatable member rotates with said projection and hole engaged with eachother, a rotational driving force is transmitted from said drivingrotatable member to said photosensitive drum through engagement betweensaid projection and said hole with said hole being pulled into saidprojection.
 76. A process cartridge according to claim 75, wherein saidhole is formed as a recess in a shaft projected outwardly in arotational axis direction from said photosensitive drum, and said shaftfunctions to rotatably support said photosensitive drum in a cartridgeframe.
 77. A process cartridge according to claim 76, wherein said shaftis substantially coaxial with a helical gear, and, at a side oppositefrom said shaft, there is provided an engaging portion for engagementwith an inner surface of said photosensitive drum, wherein said hole,helical gear, engaging portion and shaft are made of integrally moldedresin material, and the helical gear transmits driving force to adeveloping roller as said process means.
 78. A process cartridgeaccording to claim 75 or 77, further comprising a circular or arcuatewall extending around said hole, said wall functioning as a guide forengagement between said projection and hole.
 79. A process cartridgeaccording to claim 76 or 77, wherein an outer diameter D1 of saidphotosensitive drum, an outer diameter F of said shaft and a diameter Cof a circumscribed circle of said projection, satisfy:D1>F≧C.
 80. Aprocess cartridge according to claim 75 or 77, wherein said projectionhas a substantially triangular cross-section, and said hole has asubstantially triangular cross-section, and wherein corners oftriangular shapes are beveled.
 81. A process cartridge according toclaim 75, further comprising a portion to be urged by a part of the mainassembly by a spring and a portion to be contacted to a fixed portion ofthe main assembly, when said process cartridge is mounted the mainassembly.
 82. A process cartridge according to claim 75, wherein saidprocess cartridge contains said photosensitive drum, and at least one ofcharging means, developing means and cleaning means, as a unit.
 83. Anelectrophotographic image forming apparatus, for forming an image on arecording material, to which a process cartridge is detachablymountable, said apparatus comprising:a motor; a driving rotatable memberfor receiving a driving force from said motor; a twisted projectionsubstantially coaxial with said driving rotatable member, saidprojection having a polygonal cross-section; means for mounting aprocess cartridge, the process cartridge including:anelectrophotographic photosensitive drum; process means actable on saidphotosensitive drum; and a twisted polygonal hole provided at alongitudinal end of said photosensitive drum, wherein when said drivingrotatable member rotates with said projection and hole engaged with eachother, a rotational driving force is transmitted from said drivingrotatable member to said photosensitive drum through engagement betweensaid projection and said hole with said hole being pulled into saidprojection; moving means for imparting relative movement between saidprojection and said hole in a longitudinal direction of saidphotosensitive drum; and means for feeding the recording material. 84.An apparatus according to claim 83, wherein a shaft is providedsubstantially coaxial with a drum gear, and at a side opposite from saidshaft, there is provided an engaging portion for engagement with aninner surface of said photosensitive drum, wherein said hole, drum gear,engaging portion and shaft are made of integrally molded resin material,and the drum gear transmits driving force to a developing roller as saidprocess means.
 85. An apparatus according to claim 84, wherein saiddriving rotatable member and drum gear are helical gears. claim 84,wherein said main assembly side gear and drum gear are helical gears.86. An apparatus according to claim 84, wherein an outer diameter F ofsaid shaft, a diameter C of a circumscribed circle of said projection, adedendum diameter G of the drum gear and an inner diameter D2 of saidphotosensitive drum, satisfy:G>D2, and G>F≧C.
 87. An apparatus accordingto claim 83, further comprising a portion to be urged by a part of themain assembly by a spring and a portion to be contacted to a fixedportion of the main assembly, when said process cartridge is mounted tothe main assembly.
 88. An apparatus according to claim 83, wherein saidprocess means includes at least one of charging means, developing meansand cleaning means.
 89. An apparatus according to claim 83, wherein anouter diameter D1 of said photosensitive drum and dedendum diameter L ofsaid main assembly side gear satisfy: 1.0×D1≦L≦5.0×D1, approximately.90. An apparatus according to claim 83, wherein said driving rotatablemember has a module of approximately 40.4-0.7 and has a dedendumdiameter L of approximately 30-150 mm, and further has 40-400 teeth. 91.An apparatus according to claim 83, further comprising an openable coverfor permitting mounting and demounting of said process cartridgerelative to a main assembly of said image forming apparatus, whereinsaid moving means are for moving said projection away from said hole ininterrelation with opening of said cover, and are for moving saidprojection toward said hole in interrelation with closing of said cover.92. A process cartridge detachably mountable to a main assembly of animage forming apparatus, wherein said main assembly includes a motor, adriving rotatable member for receiving a driving force from said motorand a twisted projection substantially coaxial with said drivingrotatable member, said projection having a substantially triangularcross-section, said process cartridge comprising:a cartridge frame; anelectrophotographic photosensitive drum; a developing roller fordeveloping a latent image formed on said photosensitive drum; and atwisted substantially triangular hole provided at a longitudinal end ofsaid photosensitive drum, wherein when said driving rotatable memberrotates with said projection and hole engaged with each other, arotational driving force is transmitted from said driving rotatablemember to said photosensitive drum through engagement between saidprojection and said hole with said hole being pulled into saidprojection; and wherein said hole is provided at an end of a shaftsubstantially coaxial with a drum helical gear for transmittingrotational force to said developing roller, and wherein said shaftfunctions to rotatably support said photosensitive drum in saidcartridge frame.
 93. A process cartridge according to claim 92, whereinat a side opposite from said shaft, there is provided an engagingportion for engagement with an inner surface of said photosensitivedrum, and wherein said hole, drum helical gear, engaging portion andshaft are made of integrally molded resin material.
 94. A processcartridge according to claim 93, wherein corners of said hole areabeveled.
 95. A process cartridge according to claim 92, furthercomprising a circular or arcuate wall extending around said hole, saidwall functioning as a guide for engagement between said projection andhole.
 96. A process cartridge according to claim 92 or 93, wherein anouter diameter F of said shaft, a diameter C of a circumscribed circleof said projection, a dedendum diameter G of the drum helical gear ofsaid photosensitive drum and an inner diameter D2 of said photosensitivedrum, satisfy:G>D2, and G>F≧C.
 97. A process cartridge according toclaim 92, further comprising a portion to be urged by a part of the mainassembly by a spring and a portion to be contacted to a fixed portion ofthe main assembly, when said process cartridge is mounted to the mainassembly.
 98. A process cartridge according to claim 92, wherein saidprocess cartridge further comprises at least one of a charging rollerand a cleaning blade.
 99. An electrophotographic image formingapparatus, for forming an image on a recording material, to which aprocess cartridge is detachably mountable, said apparatus comprising:amotor; a driving rotatable member for receiving a driving force fromsaid motor; a twisted projection substantially coaxial with said drivingrotatable member, said projection having a substantially triangularcross-section; means for mounting a process cartridge, the processcartridge including:a cartridge frame; an electrophotographicphotosensitive drum; a developing roller for developing a latent imageformed on said photosensitive drum; and a twisted substantiallytriangular hole provided at a longitudinal end of said photosensitivedrum, wherein when said driving rotatable member rotates with saidprojection and hole engaged with each other, a rotational driving forceis transmitted from said driving rotatable member to said photosensitivedrum through engagement between said projection and said hole with saidhole being pulled into said projection, wherein said hole is provided atan end of a shaft substantially coaxial with a drum helical gear fortransmitting rotational force to said developing roller, and whereinsaid shaft functions to rotatably support said photosensitive drum insaid cartridge frame; moving means for imparting relative movementbetween said projection and said hole in a longitudinal direction ofsaid photosensitive drum; and means for feeding the recording material.100. An apparatus according to claim 99, wherein at a side opposite fromsaid shaft, there is provided an engaging portion for engagement with aninner surface of said photosensitive drum, and wherein said hole, drumhelical gear, engaging portion and shaft are made of integrally moldedresin material, and the drum helical gear transmits driving force tosaid developing roller.
 101. An apparatus according to claim 99, whereinsaid process cartridge further comprises a portion to be urged by a partof a main assembly of said image forming apparatus by a spring and aportion to be contacted to a fixed portion of the main assembly, whensaid process cartridge is mounted to the main assembly.
 102. Anapparatus according to claim 99, wherein said process cartridge containsat least one of charging roller and cleaning blade.
 103. An apparatusaccording to claim 99, wherein an outer diameter F of said shaft, adiameter C of a circumscribed circle of said projection, a dedendumdiameter G of the drum helical gear and an inner diameter D2 of saidphotosensitive drum, satisfy:G>D2, and G>F≧C.
 104. An apparatusaccording to claim 99, wherein an outer diameter D1 of saidphotosensitive drum and dedendum diameter L of said driving rotatablemember satisfy: 1.0×D1≦L≦5.0×D1, approximately.
 105. An apparatusaccording to claim 99, wherein said driving rotatable member has amodule of approximately 0.4-0.7 and has a dedendum diameter L ofapproximately 30-150 mm, and further has 40-400 teeth.
 106. An apparatusaccording to claim 99, further comprising an openable cover forpermitting mounting and demounting of said process cartridge relative toa main assembly of said image forming apparatus, wherein said movingmeans are for moving said projection away from said hole ininterrelation with opening of said cover, and are for moving saidprojection toward said hole in interrelation with closing of said cover.107. A process cartridge detachably mountable to a main assembly of animage forming apparatus, wherein said main assembly includes a motor, amain assembly side helical gear for receiving driving force from saidmotor and a twisted projection substantially coaxial with said mainassembly side helical gear, said projection having a substantiallytriangular cross-section, said process cartridge comprising:a cartridgeframe; an electrophotographic photosensitive drum; a developing rollerfor developing a latent image formed on said photosensitive drum; acleaning blade for removing residual toner from said photosensitivedrum; and a twisted substantially triangular hole provided at alongitudinal end of said photosensitive drum, wherein when said mainassembly side helical gear rotates with said projection and hole engagedwith each other, rotational driving force is transmitted from said mainassembly side helical gear to said photosensitive drum throughengagement between said projection and said hole with said hole beingpulled into said projection; and wherein said hole is provided at an endof a shaft substantially coaxial with a drum helical gear fortransmitting rotational force to said developing roller, and whereinsaid shaft functions to rotatably support said photosensitive drum insaid cartridge frame, and wherein said hole, drum helical gear and shaftare made of integrally molded resin material, and an outer diameter D1of said photosensitive drum, an outer diameter F of said shaft and adiameter C of a circumscribed circle of said hole, satisfy: D1>F≧C. 108.A process cartridge according to claim 107, wherein at a side oppositefrom said shaft, there is provided an engaging portion for engagementwith an inner surface of said photosensitive drum, and wherein saidhole, drum helical gear, engaging portion and shaft are made ofintegrally molded resin material.
 109. A process cartridge according toclaim 107, further comprising a circular or arcuate wall extendingaround said hole, said wall functioning as a guide for engagementbetween said projection and hole.
 110. A process cartridge according toclaim 107, wherein corners of said hole are beveled.
 111. A processcartridge according to claim 107, further comprising a portion to beurged by a part of the main assembly by a spring and a portion to becontacted to a fixed portion of the main assembly, when said processcartridge is mounted to the main assembly.
 112. An electrophotographicimage forming apparatus, for forming an image on a recording material,to which a process cartridge is detachably mountable, said apparatuscomprising:a motor; a main assembly side helical gear for receivingdriving force from said motor; a twisted projection substantiallycoaxial with said main assembly side helical gear, said projectionhaving a substantially triangular cross-section, and said projectionbeing formed in an end of a circular column projected from asubstantially central portion of said main assembly side helical gear;means for mounting a process cartridge, the process cartridgeincluding:a cartridge frame; an electrophotographic photosensitive drum;a developing roller for developing a latent image formed on saidphotosensitive drum; a cleaning blade for removing residual toner fromsaid photosensitive drum; and a twisted substantially triangular holeprovided at a longitudinal end of said photosensitive drum, wherein whensaid main assembly side helical gear rotates with said projection andhole engaged with each other, rotational driving force is transmittedfrom said main assembly side helical gear to said photosensitive drumthrough engagement between said projection and said hole with said holebeing pulled into said projection; and wherein said hole is provided atan end of a shaft substantially coaxial with a drum helical gear fortransmitting rotational force to said developing roller, and whereinsaid shaft functions to rotatably support said photosensitive drum insaid cartridge frame, and wherein said hole, drum helical gear and shaftare made of integrally molded resin material, and an outer diameter D1of said photosensitive drum, an outer diameter F of said shaft and adiameter C of a circumscribed circle of said projection, satisfy D1>F≧C;an openable cover for permitting mounting and demounting of said processcartridge relative to a main assembly of said image forming apparatus;moving means for moving said projection away from said hole ininterrelation with opening of said cover, and for moving said projectiontoward said hole in interrelation with closing of said cover; and meansfor feeding the recording material, wherein a dedendum diameter G of thedrum helical gear and an inner diameter D2 of said photosensitive drum,satisfy:G>D2, and G>F≧C.
 113. An apparatus according to claim 112,wherein said main assembly side helical gear has a module ofapproximately 0.4-0.7 and has a dedendum diameter L of approximately30-150 mm, and further has 40-400 teeth.
 114. A drive transmission partfor transmitting a driving force to an electrophotographicphotosensitive drum and a developing roller for developing a latentimage formed on said photosensitive drum, which are contained in aprocess cartridge detachably mountable to a main assembly of an imageforming apparatus for forming an image on a recording material, saidmain assembly including a motor, a driving rotatable member forreceiving a driving force from said motor, and a twisted projectionsubstantially coaxial with said driving rotatable member, saidprojection having a polygonal cross-section, said drive transmissionpart comprising:a gear for transmitting a driving force from said mainassembly to said developing roller when said process cartridge ismounted to the main assembly; a shaft substantially coaxial with saidgear; and a twisted polygonal hole provided at an end of said shaft,wherein said hole receives a driving force from the main assemblythrough engagement between said projection and hole, wherein the drivingforce is transmitted to said photosensitive drum through the shaft, andis transmitted to said developing roller through said gear.
 115. A partaccording to claim 114, wherein an outer diameter D1 of saidphotosensitive drum, an outer diameter F of said shaft and a diameter Cof a circumscribed circle of said projection, satisfy:D1>F≧C.
 116. Apart according to claim 114, wherein said hole, gear and shaft are madeof integrally molded resin material.
 117. A part according to claim 116,wherein said resin material is polyacetal resin, polycarbonate resin,polyamide resin, or polyethyleneterephthalate resin.
 118. A drivetransmission part for transmitting driving force to anelectrophotographic photosensitive drum and a developing roller fordeveloping a latent image formed on said photosensitive drum, which arecontained in a process cartridge detachably mountable to a main assemblyof an image forming apparatus for forming an image on a recordingmaterial, said main assembly including a motor, a main assembly sidegear for receiving driving force from said motor, and a twistedprojection substantially coaxial with said main assembly side gear, saidprojection having a substantially triangular cross-section, said drivetransmission part comprising:a helical gear for transmitting drivingforce from said main assembly to said developing roller when saidprocess cartridge is mounted to the main assembly; a shaft substantiallycoaxial with said helical gear; and a twisted substantially triangularhole provided at an end of said shaft, wherein when said main assemblyside gear rotates with said projection and hole engaged with each other,rotational driving force is transmitted from said main assembly sidegear to said photosensitive drum through engagement between saidprojection and said hole with said hole being pulled into saidprojection, and the driving force is transmitted to said photosensitivedrum through said shaft and is transmitted to said developing rollerthrough said helical gear, wherein said hole, helical gear and shaft aremade of integrally molded resin material, and an outer diameter D1 ofsaid photosensitive drum, an outer diameter F of said shaft and adiameter C of a circumscribed circle of said projection, satisfy:D1>F≧C.
 119. A photosensitive drum, which is contained in a processcartridge detachably mountable to a main assembly of an image formingapparatus for forming an image on a recording material, said mainassembly including a motor, a driving rotatable member for receiving adriving force from said motor, and a twisted projection substantiallycoaxial with said driving rotatable member, said projection having apolygonal cross-section, said photosensitive drum comprising:a cylinderhaving a photosensitive layer thereon; and a drive transmission membermounted to an end of said cylinder, said transmission member including:a gear for transmitting a driving force from said main assembly to adeveloping roller when said process cartridge is mounted to the mainassembly; a shaft substantially coaxial with said gear; and a twistedpolygonal hole provided at an end of said shaft, wherein said holereceives driving force from the main assembly through engagement betweensaid projection and hole, wherein the driving force is transmitted tosaid photosensitive drum through the shaft, and is transmitted to saiddeveloping roller through said gear.
 120. A photosensitive drumaccording to claim 119, wherein an outer diameter D1 of saidphotosensitive drum, an outer diameter F of said shaft and a diameter Cof a circumscribed circle of said projection, satisfy:D1>F≧C.
 121. Aphotosensitive drum according to claim 119, wherein said hole, gear andshaft are made of integrally molded resin material.
 122. Aphotosensitive drum according to claim 121, wherein said resin materialis polyacetal resin, polycarbonate resin, polyamide resin, orpolyethyleneterephthalate resin.
 123. A photosensitive drum according toclaim 119, wherein a spur gear is mounted to an end of said cylinder,and wherein said spur gear functions to transmit a driving force forrotating an image transfer roller.
 124. A photosensitive drum, which iscontained in a process cartridge detachably mountable to a main assemblyof an image forming apparatus for forming an image on a recordingmaterial, said main assembly including a motor, a main assembly sidegear for receiving driving force from said motor, and a twistedprojection substantially coaxial with said main assembly side gear, saidprojection having a polygonal cross-section, said photosensitive drumcomprising:a cylinder having a photosensitive layer thereon; and a drivetransmission member mounted to an end of said cylinder, saidtransmission member including:a helical gear for transmitting drivingforce from said main assembly to a developing roller of said processcartridge when said process cartridge is mounted to the main assembly; ashaft substantially coaxial with said helical gear; and a twistedsubstantially triangular hole provided at an end of said shaft, whereinwhen said main assembly side gear rotates with said projection and holeengaged with each other, rotational driving force is transmitted fromsaid main assembly side gear to said photosensitive drum throughengagement between said projection and said hole with said hole beingpulled into said projection, and the driving force is transmitted tosaid photosensitive drum through said shaft and is transmitted to saiddeveloping roller through said helical gear, wherein said hole, helicalgear and shaft are made of integrally molded resin material, and anouter diameter D1 of said photosensitive drum, an outer diameter F ofsaid shaft and a diameter C of a circumscribed circle of saidprojection, satisfy:D1>F≧C, and wherein a spur gear is provided, at anend of said cylinder, for transmitting the driving force for rotating animage transfer roller in the main assembly when said process cartridgeis mounted to the main assembly.
 125. A process cartridge detachablymountable to a main assembly of an image forming apparatus for formingan image on a recording material, said main assembly including a motor,a driven rotatable member for receiving driving force from said motorand a twisted recess or projection having a non-circular cross-sectionand substantially coaxial with a rotation axis of said driven rotatablemember, said process cartridge comprising:a rotatableelectrophotographic photosensitive drum; process means actable on saidphotosensitive drum; and a twisted projection or recess provided at alongitudinal end of said photosensitive drum, having a non-circularcross-section and substantially coaxial with a rotation axis of saidphotosensitive drum, wherein said projection or recess of saidphotosensitive drum has such a dimension and configuration that saidprojection or recess can take a first relative rotational position withrespect to said recess or projection of said driven rotatable member inwhich relative rotational movement therebetween is permitted, and asecond relative rotational position with respect to said recess orprojection of said driven rotatable member in which relative rotationalmovement is prevented in one rotational direction, while the rotationaxis of said driven rotatable member and the rotation axis of saidphotosensitive drum are substantially aligned.
 126. A process cartridgeaccording to claim 125, wherein said recess or projection of said drivenrotatable member and said projection or recess of said photosensitivedrum are contacted substantially at three twisted lines.
 127. A processcartridge according to claim 126, wherein said three twisted linesconstitute a substantially equilateral triangle.
 128. A processcartridge detachably mountable to a main assembly of an image formingapparatus, wherein said main assembly includes a motor, a drivingrotatable member for receiving a driving force from said motor and ahole defined by twisted surfaces, said hole being substantially coaxialwith said driving rotatable member, said process cartridge comprising:anelectrophotographic photosensitive drum; process means actable on saidphotosensitive drum; and a twisted projection engageable with saidtwisted surfaces, said projection being provided at a longitudinal endof said photosensitive drum, wherein, when said driving rotatable memberrotates with said hole and projection engaged with each other, arotational driving force is transmitted from said driving rotatablemember to said photosensitive drum through engagement between said holeand said projection.
 129. A process cartridge according to claim 128,wherein said projection is projected from an end of a shaft projectedoutwardly in a rotational axis direction from a said photosensitivedrum, and said shaft functions to rotatably support said photosensitivedrum in a cartridge frame.
 130. A process according to claim 129,wherein an outer diameter D1 of said photosensitive drum, an outerdiameter F of said shaft, and a diameter C of a circumscribed circle ofsaid projection, satisfy:D1>F≧C, and wherein said projection and shaftare of integrally molded resin material.
 131. A process cartridgeaccording to claim 129, wherein an outer diameter F of said shaft, adiameter of C of a circumscribed circle of said projection, a dedendumdiameter G of the gear of said photosensitive drum and an inner diameterof said photosensitive drum D2, satisfy:G>D2, and F>G≧C, and whereinsaid projection, said shaft and said drum gear are composed ofintegrally molded resin material.
 132. A process cartridge according toclaim 128, 130 or 131, wherein said hole has a substantially triangularcross-section with beveled, triangular-shaped corners, and saidprojection has a substantially triangular cross-section with beveled,triangular-shaped corners.
 133. A process cartridge according to claim128, wherein said process means includes at least one of charging means,developing means, and cleaning means as a unit.
 134. A drivetransmission part, for transmitting a driving force to anelectrophotographic photosensitive drum and a developing roller fordeveloping a latent image formed on said photosensitive drum, usablewith an electrophotographic image forming apparatus for forming an imageon a recording material, said apparatus including a motor, a drivingrotatable member for receiving a driving force from said motor, and ahole defined by twisted surfaces, said hole being substantially coaxialwith said driving rotatable member, said drive transmission partcomprising:a transmission part gear for transmitting a driving force tosaid developing roller; a shaft substantially coaxial with saidtransmission part gear; and a twisted projection engageable with saidtwisted surfaces, said projection being provided at an end of saidshaft, wherein said projection receives a driving force from saiddriving rotatable member through engagement between said hole and saidprojection, and wherein the driving force is transmitted to saidphotosensitive drum through the shaft, and is transmitted to saiddeveloping roller through said transmission part gear.
 135. A drivetransmission part according to claim 134, wherein said projection, saidtransmission part gear, and said shaft are composed of integrally moldedresin material.
 136. A drive transmission part according to claim 134 or135, wherein said hole has a substantially triangular cross-section withbeveled, triangular-shaped corners, and said projection has asubstantially triangular cross-section with beveled, triangular-shapedcorners.
 137. A drive transmission part according to claim 136, whereinan outer diameter F of said shaft, a diameter C of a circumscribedcircle of said projection, a dedendum diameter G of said transmissionpart, and an inner diameter of said photosensitive drum D2,satisfy:G>D2, and G>F≧C.
 138. A drive transmission part according toclaim 137, wherein said projection receives an attraction forceattracting it into the hole when said projection transmits a rotationalforce to the photosensitive drum while being in engagement with thehole.
 139. A photosensitive drum, usable with an electrophotographicimage forming apparatus for forming an image on a recording material,said apparatus including a motor, a driving rotatable member forreceiving a driving force from said motor, and a hole defined by twistedsurfaces, said hole being substantially coaxial with said driving, saidphotosensitive drum comprising:a cylinder having a photosensitive layerthereon; and a drive transmission member mounted to an end of saidcylinder, said transmission member including:a transmission member gearfor transmitting a driving force from said driving rotatable member to adeveloping roller; a shaft substantially coaxial with said transmissionmember gear; and a twisted projection engageable with said twistedsurfaces, said projection being provided at an end of said shaft,wherein said projection receives a driving force from said drivingrotatable member through engagement between said hole and saidprojection, and wherein the driving force is transmitted to saidphotosensitive drum through the shaft, and is transmitted to saiddeveloping roller through said transmission member gear.
 140. A drumaccording to claim 139, wherein an outer diameter D1 of saidphotosensitive drum, and an outer diameter F of said shaft, and adiameter C of a circumscribed circle of said projection, satisfy:D1>F≧C,andwherein said projection and shaft are composed of integrally moldedresin material.
 141. A drum according to claim 139, wherein an outerdiameter F of said shaft, a diameter C of a circumscribed circle of saidprojection, a dedendum diameter G of a gear of the transmission membergear, and an inner diameter of said photosensitive drum D2,satisfy:G>D2, and G>F≧C, andwherein said projection, said shaft and saidtransmission member gear are composed of integrally molded resinmaterial.
 142. A drum according to claim 139, wherein said transmissionmember gear, said shaft and said projection are composed of integrallymolded resin material.
 143. A drum according to claim 139, 140, 141, or142, wherein said hole has a substantially triangular cross-section withbeveled, triangular-shaped corners, and said projection has asubstantially triangular cross-section, with beveled, triangular-shapedcorners.
 144. A drum according to claim 143, wherein said projectionreceives an attraction force attracting it into the hole when saidprojection transmits a rotational force to the photosensitive drum whilebeing in engagement with the hole.
 145. A process cartridge detachablymountable to a main assembly of an image forming apparatus for formingan image on a recording material, said main assembly including a motor,a driving rotatable member for receiving driving force from said motorand having a twisted recess or projection having a non-circularcross-section and being substantially coaxial with a rotation axis ofsaid driving rotatable member, said process cartridge comprising:arotatable electrophotographic photosensitive drum; process means actableon said photosensitive drum; and a twisted projection or recess providedat a longitudinal end of said photosensitive drum, having a non-circularcross-section and being substantially coaxial with a rotation axis ofsaid photosensitive drum, wherein said projection or recess of saidphotosensitive drum has such a dimension and configuration that saidprojection or recess of said photosensitive drum can take a firstrelative rotational position with respect to said recess or projectionof said driving rotatable member in which relative rotational movementtherebetween is permitted, and a second relative rotational positionwith respect to said recess or projection of said driving rotatablemember in which relative rotational movement is prevented in onerotational direction, while the rotation axis of said driving rotatablemember and the rotation axis of said photosensitive drum aresubstantially aligned, and the photosensitive drum is urged in alongitudinal direction of said photosensitive drum by engagement betweenthe recess or projection of the driving rotatable member and saidprojection or recess of said photosensitive drum.
 146. A processcartridge detachably mountable to a main assembly of an image formingapparatus for forming an image on a recording material, said mainassembly including a motor, a driving rotatable member for receivingdriving force from said motor and having a twisted recess or projectionhaving a non-circular cross-section and being substantially coaxial witha rotation axis of said driving rotatable member, said process cartridgecomprising:a rotatable electrophotographic photosensitive drum; processmeans actable on said photosensitive drum; and a twisted projection orrecess provided at a longitudinal end of said photosensitive drum,having a non-circular cross-section and being substantially coaxial witha rotation axis of said photosensitive drum, wherein said projection orrecess of said photosensitive drum has such a dimension andconfiguration that said projection or recess of said photosensitive drumcan take a first relative rotational position with respect to saidrecess or projection of said driving rotatable member in which relativerotational movement therebetween is permitted, and a second relativerotational position with respect to said recess or projection of saiddriving rotatable member in which relative rotational movement isprevented in one rotational direction by engagement between the twistedrecess or projection of the driving rotatable member and said twistedprojection or recess of said photosensitive drum, while substantiallyaligning the rotation axis of said photosensitive drum with the rotationaxis of said driving rotatable member and urging the photosensitive drumin a longitudinal direction of said photosensitive drum by engagementtherebetween.